two errors messages preventing opening LR

The message: “...issue with AI edits. Future edits may not be saved...” is a known issue in LrC version 15.x. The old form contained a thread regarding this problem. But unfortunately this thread has been migrated to the new forum at the moment.  

Here is a answer of ​@Rikk Flohr_Photography from this thread:

Contacting support is your best course of action. The failure you are seeing is not new to version 15.1, but it formerly had no dialog to display when it occurred. The Error Message was added in LrC version 15.1 to guide you toward a workable solution. If you encounter this new dialog, you should:

 

1.  Review this document:  https://helpx.adobe.com/lightroom-classic/kb/ai-edits-storage-error.html to make sure you are not affected by the items listed there. 
   2.  Contact Adobe Support as they have an lrcat-data recovery tool that can fix your corrupt file.
   
   You would do this if you don't want to take the extreme option of removing your lrcat-data file and rebuilding it from scratch, as has been mentioned in this thread. This method works, but it can result in unexpected results when AI data has been recalculated.  

Please note that the understood causes of corruption in this file are external. It is essential to review this KB document to ensure you don't have future corruption. 

Thank you for your patience. 

Contact Adobe Customer Care at  https://helpx.adobe.com/contact/what-contact-options.html. Scroll to the bottom and click on the “Start Now” live chat link in the lower right of this page. Typing “Agent” into the chat text field will bypass the initial chatbot.

Rikk Flohr: Adobe Photography Org

According the second message it seems that there’s an issue with the preview cache. Delete the cache and check.

Lightroom error on preview cache or displays gray thumbnails