in the other thread on this subject, Rachel answered as follows. Worked for me! Cheers
Re: iOS touch ID duration
Could you double check these settings in the LastPass app?
In the LastPass app, go to Settings > Security > adjust the Lock Options and Auto Logout settings (and make sure the Log Out on Close option is also turned off.) The Lock Options setting is how often you'd like to have the LastPass app require Face ID/PIN code/Touch ID verification, and the Auto Logout setting is how often the LastPass app will fully log out and require the master password to log in. For example, if you only want to have to use biometrics to unlock the LastPass app, you would set Auto Logout to Never and change the Lock Options to your desired time period--for example, you can set Lock Options to 24 hours to be prompted for biometric authentication every 24 hours.
If these settings are set correctly as explained above, we would recommend uninstalling the LastPass app, restarting your device, then reinstalling and re-enabling the above settings to your preference to see if that resolves this issue.
I found several support threads dealing with these options, and it does seem to solve the problem for some users. The reason I created this thread is because LP was locking me out despite following the tips you posted. If you check my first post you will see that I've already tried all of the things you suggested.
If/when the problem returns on my iPhone 12 I will definitely try reinstalling the app!