Authentication failed when cloning a repository to the server, another repository works fine

Hello,

I have a “group” and I am the owner of it, I have two subgroups under it, and a project in each subgroup.
So I have all the permissions needed to clone them.

So on my server I have a private key, and the public key is my account on Gitlab. When I try to clone one project of the two, I get the following errors:

Using ssh:

GitLab: The project you were looking for could not be found.
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

I tried using HTTPS but it says it needs an API key and honestly even if that works I don’t really want to use it in the future.

The strange thing is that the other repository can be cloned just fine using the same key pair.
I am copying the SSH link provided by Gitlab from the project page.

I should mention that the project I can clone was created months ago, while the new one was created few days ago. Maybe something changed with cloning permission?

Thanks in advance.