Unable to run dmg file for V 6.1.5 on Mac "Image not recognised"

Trying to upgrade to V6.1.5 on 2 iMacs - one running Mojave OSX 10.14.3 , the other High Sierra 10.13.6 - I get the message “Image not recognised” when attempting to run the downloaded LibreOffice 6.1.5 dmg files in both cases.
Can anyone provide a solution ? Thanks

Did you check any of SHA256, SHA1 or MD5 to verify the integrity of the files you downloaded?

Metadata for http://download.documentfoundation.org/libreoffice/stable/6.1.5/mac/x86_64/LibreOffice_6.1.5_MacOS_x86-64.dmg

SHA-256 Hash: 1f4a1f5cb8ec2afcf53c7b87fdb978f02e7ad727613622e6fc578410746d565c

SHA-1 Hash: a54e4af9807284ce084fc9f582264aeca8ae1400

MD5 Hash: 0435eff25acf163e007e69111f661b2f

NO - How do I do this ? Thanks

Check here https://www.dyclassroom.com/howto-mac/how-to-verify-checksum-on-a-mac-md5-sha1-sha256-etc

Briefly: On the command line perform (one of)

$ md5 /path/to/file
$ shasum -a 1 /path/to/file
$ shasum -a 256 /path/to/file

Thanks anyway Opaque

Simple solution - the above happened after double clicking the file. However, Right clicking the file and Opening with the Disk manager things proceeded as normal.