SQL Management Studio only connects remotely without the instance

Question

While trying to make a connection with a first remote SQL, I realized that my Management Studio could not connect using the instance, as follows:

After that attempt, I removed the instance, and since this server only has one SQL, it took the default system, and logged out normally without the instance:

Now my problem is that I am trying to connect to a database that has multiple instances, and my SQL generates the following error:

Assuming I test without the instance, it generates a login error as it does not find my user and password in the default database.

I already changed the version of my Management Studio to 2014 (I was using 2017) I already formatted my computer last night I installed again Management Studio 2017

And so far, I’ve had absolutely no success. Has anyone been through the same problem, or would have some idea of a solution?