After installing the add-ons I've tried to open the c3P files, but the same message keeps popping out.
"Failed to open project. Check it is a valid Construct 3 single-file (.c3p) project"
Any idea what may be happening?
Viewing post in Construct 3 3DObject Plugin - SDK V1 only comments
I am not sure why, I tried it in an incognito window and installed the latest addon and the Meshpoint example file and it worked fine. When you see this error, can you open the javascript console and see what errors are reported, a screencap will help me see what is happening. Which version of C3 are you using?
The latest, I just updated it.
After a lot of testing I managed to open it, running the browser with administrative rights solved it.
However, it's kind of weird that only your demos presented these issues.
The chrome console sent this kind of errors; I'm leaving those here in case you find it helpful.

Thank you very much for your fast and kind reply, you're the best.