Each time I invite to collaborate, it says “Could not find a GitHub account matching user”, while the accounts exist. Someone please suggest any solution.
Could you try using the email address instead of the username to find out whether it’s the same?
also, Github limits the number of people who can be invited to a repository within a 24-hour period. If you exceed this limit, either wait 24 hours or create an organization to collaborate with more people.
it might be that it is an Org you are adding not a user, if you can send screenshots of that so we can help more
It seems it was a temporary issue. Now I can send the invitation. Thank you all for your replies and support.