Hi @Juanjo_Martin_Cara and welcome to the MongoDB Forums!
Just tried it on an AWS, free tier M0 cluster and I’m able to select my cluster. I just went through these two screens:
And then:
Can you try to create a new project in your organization, then create a new free cluster in a different cloud provider / region to find the root cause of the error?
Again, welcome to the MongoDB community and hope this helps!