I had not got this warning prior to upgrading to Hub 5 Nextcloud version 27.0.0.
straight after upgrading, I saw the warning
“Invalid private key for encryption app. Please update your private key password in your personal settings to recover access to your encrypted files”
I went into Administration/overview to check and saw the same warning.
I had not set or configured any private keys and when I go to personal settings I’m required to remember a previous password that I never set before setting a new password. I feel this is happening because of changes or new features in 27.0.0 and there needs to be more obvious and clear information on this issue. The warning that you may lose your encrypted data if you cannot remember a non-existent previous password is very worrying.