I’ve got no idea how to pursue this. The document appears to me to be valid. LibreOffice Calc opens it just fine. Excel complains. So I try the Online validator. Rather than telling me what, if anything is wrong, the validator dumps stack.
export.ods: Fatal: A qualified name was required, but ‘manifest’ was given! java.lang.IllegalArgumentException: A qualified name was required, but ‘manifest’ was given! at org.odftoolkit.odfdom.pkg.OdfNamespace.splitQName(OdfNamespace.java:142) at org.odftoolkit.odfdom.pkg.OdfNamespace.getPrefixPart(OdfNamespace.java:154) at org.odftoolkit.odfdom.pkg.OdfName.newName(OdfName.java:82) at org.odftoolkit.odfdom.pkg.OdfFileDom.createElementNS(OdfFileDom.java:298) at org.odftoolkit.odfdom.pkg.OdfFileSaxHandler.startElement(OdfFileSaxHandler.java:82) at org.odftoolkit.odfdom.pkg.rdfa.MultiContentHandler.startElement(MultiContentHandler.java:76) at org.apache.xerces.parsers.AbstractSAXParser.startElement(Unknown Source) at org.apache.xerces.impl.XMLNSDocumentScannerImpl.scanStartElement(Unknown Source) at org.apache.xerces.impl.XMLNSDocumentScannerImpl$NSContentDispatcher.scanRootElementHook(Unknown Source) at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(Unknown Source) at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source) at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source) at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source) at org.apache.xerces.parsers.XMLParser.parse(Unknown Source) at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source) at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source) at org.odftoolkit.odfdom.pkg.OdfFileDom.initialize(OdfFileDom.java:236) at org.odftoolkit.odfdom.pkg.OdfFileDom.initialize(OdfFileDom.java:212) at org.odftoolkit.odfdom.pkg.manifest.OdfManifestDom.initialize(OdfManifestDom.java:73) at org.odftoolkit.odfdom.pkg.OdfFileDom.(OdfFileDom.java:132) at org.odftoolkit.odfdom.pkg.manifest.OdfManifestDom.(OdfManifestDom.java:64) at org.odftoolkit.odfdom.pkg.OdfFileDom.newFileDom(OdfFileDom.java:194) at org.odftoolkit.odfdom.pkg.OdfPackage.parseManifest(OdfPackage.java:1313) at org.odftoolkit.odfdom.pkg.OdfPackage.readZip(OdfPackage.java:549) at org.odftoolkit.odfdom.pkg.OdfPackage.initializeZip(OdfPackage.java:519) at org.odftoolkit.odfdom.pkg.OdfPackage.(OdfPackage.java:328) at org.odftoolkit.odfdom.pkg.OdfPackage.loadPackage(OdfPackage.java:439) at org.odftoolkit.odfvalidator.ODFStreamValidator.getPackage(ODFStreamValidator.java:52) at org.odftoolkit.odfvalidator.ODFRootPackageValidator.getPackage(ODFRootPackageValidator.java:59) at org.odftoolkit.odfvalidator.ODFPackageValidator._validate(ODFPackageValidator.java:99) at org.odftoolkit.odfvalidator.ODFPackageValidator.validate(ODFPackageValidator.java:84) at org.odftoolkit.odfvalidator.ODFValidator.validateStream(ODFValidator.java:211) at org.apache.jsp.jsp.validate_jsp._jspService(validate_jsp.java:232) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329) at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:712) at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:580) at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:516) at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:955) at org.apache.jsp.jsp.index_jsp._jspService(index_jsp.java:128) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329) at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:688) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:367) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1639) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.base/java.lang.Thread.run(Thread.java:834)