Currently working with two GitLab accounts, one mine and one for the research group I am working for. I have a problem with pushing projects to the research group account. Git says I don’t have permission.
I haven’t done what you’re trying to do, so there’s a limit to my knowledge on what is possible.
But you problems might not even be due to GitLab. Do you ssh-agent and have added both your keys? Then ssh has a hard time figuring out which key to use against gitlab (especially as it’s the same address you’re connecting to), there is some option to make it ignore the availability of some key (I don’t remember what option it was, but I do remember that ‘-i’ didn’t work, it only adds a key to the list of available keys, it doesn’t specify that you want to use that key).
If the above isn’t your problem, maybe try to provide us with a full transcript (input and output) of your attempted interaction with GitLab.