I have selected in "Enpass 5" - Backup and saved it to my drive.

In "Enpass 6" I select "Restore" and select the backup file.
Now I am asked for my password. After a long time, about 30 seconds, I get the message "Incorrect password."

I found the same - but after restarting Enpass 6 the vault had been loaded correctly. However, also had on a couple of occasions Enpass 6 crashes at the end of the import - but again if you restart the app, the vault is loaded ... Windows 10 64bit [Version 10.0.17134.112]

I had the same problem. Also, Enpass6 apparently created multiple vaults for every try to enter the password:

Hey guys,

Thanks for reporting these issues. We have tracked the issue and a fix will be available in the next update.

Thanks for your co-operation and keep reporting.