LrC will not open

1. Ok, an issue to look at, that I think you may have overlooked.   Rob_Cullen noticed that you appear to be keeping your catalog on a One Drive share on the cloud. A LrC catalog must be on a actual hard drive in or connected to your computer. Can you verify where your catalog is stored?

2. A recommendation, and an experiment, this apply's to Windows users, not so much Apple. At one time, MS had a issue that affected a few users, and it fouled up the default Pictures "folder". For an experiment, both to get away from OneDrive if that is what is occurring, and to eliminate a possible rare Windows issue, create a new separate folder for your LrC catalog(s), perhaps call it "My Photography". Copy as much as you like from that folder you have shared (well not the backup)to this new folder, one catalog and it's associated folders will do. Then double click on that catalog. Note that a problem will occur involving photo locations, that can be fixed. Note that I said copy.

Some references that will be to point:

Lightroom Classic catalog FAQ:Adobe

How do I use my Lightroom catalog on multiple computers?: Lightroom Queen

Q&A: Why Does Lightroom Classic Upgrade My Catalog?: Mastering Lightroom.

 got a popup that said LrC would need to restart in order to open with the new catalogue. Then this came up on my desktop:

So, what one of those catalogs did you try to open? And the V11 one, is that the result of the attempt?

Ok, re-read your statement, you tried to open up;

Lightroom.catalog

I bet that one was very old.

Another point of contention, and a warning

Is that where you keep your backups?

Backups should not be on the same place as the catalogs. If this was a hard drive, and the hard drive bit the dust, not only the catalog but the backup of the catalog would be gone. Backups to separate hard drives, be they internal, external, or the cloud.

Some do keep the backup oin the cloud. Not an issue, some on a NAS, not an issue, most on an external hard drive or two, even three (second locked up in hiding from theft, third somewhere else in case of natural disaster, but that's overkill for home use)  Bit not in the same location as the working catalog.

Second, you have at least seven catalogs. Hmm, and one that would match one of those lock files does not exist (but very old)

Also note, you have the file extensions for the catalogs not showing, that would be .lrcat

Some are clearly going back to v5. Some (well the Lightroom Catalog one, maybe older. that one without a monkier attached may be a default catalog that you my have never actually used)

The one called Lightroom Catalog-v11 is probably the latest one, and is probably associated with LrC v11. When LrC has a major upgrade (as opposed to a normal update) LrC needs to create a new copy of the older catalog, and creates a fresh new one from that as the database engine will have evolved to the point that a new catalog structure is required. And unless you tell ikt otherwise, it will add the new version (in this case 11) to the new catalog name. Looks like you either went straight from v5 to v11, or cleaned out old v6, v7, etc ones.

Get all your Lightroom files out of OneDrive!!  Stop using OneDrive for Lightroom files.

Lightroom-Classic cannot work when files are only online!

Blue cloud icon:

A blue cloud icon next to your OneDrive files or folders indicates that the file is only available online. Online-only files don’t take up space on your computer.

Your catalog files that ends in v11 may be your latest (highlighted in green below)- but I cannot be sure of that. You also have two other older? Catalogs {Lightroom Catalog.lrcat} and {Lightroom 5 Catalog.lrcat}

A ".LOCK" file will prevent a catalog from opening! LOCK FILE DELETION - LR-CLASSIC 

Ok, lots to discuss. First up the lock files. When you launch LrC, for any catalog, it creates a lock file. THis lock file is to prevent multiple instances of the catalog from being opened at the same time. When you properly exit LrC, that lock file gets deleted. If you force quit LrC, or LrC crashes, the lock file does not get deleted. If yo try to open an LrC catalog that still has a lock file associated to it, a lock file that still exists then LrC will not open that catalog, some get an error message stating the catalog is in use, some get nothing, LrC, just does not start.

From your screenshot:

So you have four ;ock files, ech for a different catalog. You can (carefully) delte them.

ref:

https://helpx.adobe.com/lightroom-classic/kb/lightroom-error-catalog-cannot-be-opened-lrcat-lock.html