I've moved PST files for clients to new computers and have never had this issue.
Summary: kept getting pop-up to enter my password in my own Outlook -- I entered and ensured save was checked, verified and good connections for 'that' session. Then failed connections again later. Yes, I confirmed password correct by using ISP's web client. Updated info in Control Panel -> Mail settings -- and again, good for 'that' time and again, failed connections. Send/receive failing with ISP later -- checked CP -> Mail settings, password missing!! Re-entered in that area, test successful, and again, good for that session. Even after a restart, failing again until I enter the blanked out password in the PST (yup, that was missing!!)
Followed recommendation from this link: https://answers.microsoft.com/en-us/msoffice/forum/all/outlook-will-not-save-my-email-account-password/6aa814ee-09fa-4230-a033-025ce471d59a . Again, temp fix, still not saving password.
Ran a full Windows Security scan -- no issues. Ran a full Malwarebytes Premium scan -- no issues.
NOW -- same issues going on with a customer of mine that I had to move their app to a new computer. SO -- long story short, it's not just my computer.
BTW -- started with my 2019 Outlook install. ISP tech recommended uninstalling and try again. I uninstalled my 2019 and installed 2016 -- did NOT fix the issue. Customer is currently running 2013.