Thank you for your reply. My question is as follows: I never deleted any data or changed the location of the data. I opened Zotero again several days later and found that all the data was missing. It was like opening a new user, trying to restart and log in again to synchronize the data to no avail. Hope the authorities can provide a solution.
OK, then see Locating Missing Zotero Data, and if you're still having trouble provide the requested info. But as explained there, this usually means you deleted the data accidentally while trying to clear disk space.
Note that you do have data online, so if you did delete your data by mistake and what you have online is up to date, you can just sync to pull it down to the empty library.
Upgrade Storage
Note that you do have data online, so if you did delete your data by mistake and what you have online is up to date, you can just sync to pull it down to the empty library.