I have now made all volumes use the SHA-512 hash algorithm and they mount successfully. Thanks again for your help Enigma2Illusion.
Thanks Enigma2Illusion. I’ve had a quick look and one of the volumes uses the deprecated HMAC-RIPEMD-160 Hash Algorithm. I will look again in slower time and post back.
When I run VeraCrypt 1.26.15 (64bit) on my Windows 11 PC I find that containers created in VeraCrypt 1.23 Hotfix-2 (64 bit) on my Windows 10 PC will not mount in the VC 1.26.15/Win 11 when copied from the hard drive on the Win 10 PC. However, containers on two flash drives created in VC 1.23/Win10 will mount in VC 1.26/Win 11. I still have the install file for VC 1.23 Hotfix-2 which appears OK for Win 11 so I am now using that combination and successfully mounting each of the containers. Should I...