I'm not sure what you mean here. Uploading your database to the repair tool wouldn't have any effect on your data unless you actually moved the database file somewhere, in which case Zotero would pull down the data from your online library.

Other than a few items in the trash, nothing has been deleted recently in your online library.

My zotero.sqlite is 181.2 Mb when the max. to load in the DB repair tool is 150 Mb. What would be your suggestion? Do you consider this may be contributing to the lost references I previously mentioned? Thanks.

It is my pleasure trying to clarify what´s going on:
1. First, April 20th (“Library not opened” discussion), I contacted Zotero because I was not able to load my database and it was frozen at a screen with no references loaded. That error was not solved neither by leaving the programe and enter into it again, no matter how many times I did it nor by restarting my computer.
2. According to your help, using the Repair tool, my database was no longer frozen at that screen and loaded.
3. Then, I thought to sync my library at Zotero, but I was not successful and 11 days ago, I started the “Error while syncing” thread.
4. After using the debug tool as suggested and summarized in that discussion, I thought everything was fixed and my database was finally syncing.
5. However, I was informed that three references were not loaded. That was not so bad. But later, I realized that some collections in my library were empty and no references belonging to 2023 were loaded, as you can check pairing the repaired and my uploaded library. So, I returned to my back-up library, that as expected is not able to sync.
6. Then, I opened a new thread (“Recovered references” discussion on May 3rd).

I hope this shed light to this situation.
But still, I don´t know what to do.
Thanks for your time and help.

Currently, I do have all the references but keep on being not able to sync using the button (arrow) at the upper right corner.