Quicken does not remember last used data file name
Also check if Windows
Defender feature Ransomware protection is enabled.
If so, configure it to add Quicken as an "allowed app" without
turning off Ransomware protection:https://community.quicken.com/discussion/7857675/faq-windows-defender-controlled-folder-access
Is L:\ a mapped drive?
Have you tried moving your Quicken data file to C:\Users\,Username>\Documents\Quicken?
Answer: No due to that is irrelevant seeing is on my other two PCs Quicken data file is located on other drives/directories then C:\Users\,Username>\Documents\Quicken and they work fine.