Lightroom catalog error

Most likely the previews.lrdata are not the problem, but you can easily try that. Remove the entire previews.lrdata from the catalog folder and see if that solves the problem. If it does, then Lightroom will simply rebuild the previews.lrdata. If your problem persists, then it is really the catalog file itself.

Edit: Sorry, I just noticed that Victoria already ruled that out anyway.

I don't have backup for this catalog.

That's unfortunate, because the likelihood is that this catalog cannot be opened, and the only solution I know of (which does not apply to you) is to use a recent backup.

I strongly recommend that you begin making regular and automatic backups of your catalog file(s) — and regular and automated backups of your photo files as well — and while we are on the topic of backups, any important file (even if it has nothing to do with Lightroom) needs to be backed up. No excuses.

Backups must be stored on a different physical disk than the working version of your files.

Thread moved to Lightroom Classic forum. 

I've looked at the catalog you sent via my own website. It's not the previews causing the error, as it wouldn't open for me either. Paul has replied to your email.