Has this ever happened to you?
We generally only see errors on that page for one of three reasons. Let’s go through them:
You don’t have administrative permission at the git provider for the repository in question. This is required to link a repo via our UI. If you don’t have those permissions, working with someone with that access, you can instead link via our Command Line Interface (CLI)
You have an ad-blocking-type browser plugin that inhibits our communication with your git provider. Try incognito mode, also known as private window, to get around this. Or, switch off your ad blocker while you create a site. You’re less likely to run into problems in daily use of Netlify’s admin UI than you are during site creation specifically, so you don’t need to leave that setting disabled to host a website with us!
You have a repository at GitLab that is "deeply nested" - part of a group that is part of an organization, for instance. We are unable to support such deeply-nested repos at this time. One subgroup works, but unfortunately no more than that. If you can’t reorganize your repos structure, maybe you could host the repo on its own and connect it to Netlify via our CLI tool mentioned above?
If you still have questions, create a new topic and link this thread!