I cannot open LR classic. Message "Lightroom catalog - 2 cannot be opened because another application already has it opened" Help please.

Could you please see where your catalog is located?
Do you see any file with .lock extension?

Thanks,
Sunil

Move the both files selected above to another location and try to start Lightroom again. (The name of your catalog may be different). When LR does start again, you can delete those two moved files.

It's better not to move the -wal file. That file won't stop Lightroom from opening the catalog and it might be needed to repair the catalog. Just move the -lock file. That is the file that tells other applications that Lightroom has opened the catalog, and if that file isn't deleted upon quit (because Lightroom didn't quit correctly) then it stops Lightroom from opening the catalog again.

Thank you. Your advice worked perfectly.

I am having this same issue and when I try to move the .lrcat.lock file I get an error that reads

"The Finder can’t complete the operation because some data in “Lightroom Catalog-2.lrcat.lock” can’t be read or written.
(Error code -36)

As LR 7.2. crashes very frequently at my system I have this issue very often when trying to restart LR. Sometimes the *.lock and *.wal files are write protected and connot be deleted or moved. So I even have to restart my entire PC (win 7)!
Very annoying.