mapi_e_failure sending files in Calc

I am using Windows 10 and Mozilla TB as an email client. I keep getting MAPI_E_FAILURE error when trying to attach files from Calc (spreadsheets). It was working fine until yesterday…ran FIXMAPI.exe but did not help…when I searched for Mapi32.dll I found four of them!! Help please

Eleanor

I am using TB 69.9.0 32 bit…I thought I was using 64 bit…how do I change??