I recently encountered the same problem with opening Studio files by double-clicking. (I reinstalled Windows and upgraded to Studio 2021 last weekend.)

Here is what I eventually found in the Knowledgebase:

https://gateway.rws.com/csm?id=kb_article_view&sysparm_article=KB0039884

The article provides links to registry files that change all of the file associations for Studio.

Worked for me :-)

Sorry, I should have mentioned that the registry files are only for English and German Windows operating systems.

Judging from the screenshot above, your Windows operating system is in French.

Maybe someone from SDL/RWS can help find an equivalent registry file for French Windows.

Okay, another interesting update: I took a quick look at the English and German Studio 2021 registry files for 64-bit Windows and saw no differences.

So I copied the two registry files to Excel and used a formula to do a line by line comparison.

I might have made a mistake somewhere, but it looks like the English and German registry files are exactly the same.

How bizarre!

Maybe someone from SDL/RWS could comment on whether the English and German registry files are the same and whether the French registry file would also be the same.

Okay, another interesting update: I took a quick look at the English and German Studio 2021 registry files for 64-bit Windows and saw no differences.

So I copied the two registry files to Excel and used a formula to do a line by line comparison.

I might have made a mistake somewhere, but it looks like the English and German registry files are exactly the same.

How bizarre!

Maybe someone from SDL/RWS could comment on whether the English and German registry files are the same and whether the French registry file would also be the same.