When you try to search your friend ID (Line use user id instead of phone number — Whatsapp case– as LINE’s username) via Search by ID to often, that would trigger a LINE protection system that you been marked as activity that might try to abuse the system (spammer usually want to add as many as ID then try to send spam message to all of them). That’s why the Max limit error message shown up.
How to resolve this issue? The good news is, LINE only shutting down the “Search by id” features for about one hours. Yes, the answer for those solution would be: You just need to wait till the LINE system unlock the function of Search by id for one hours. Then you can try it again. Easy, isn’t.
Note: I guess, if the number of persons who want to try to abuse are increasing, the time of shutting down the Search by id would increase. It could be 2 or even 24 hours. That’s depend on the behaviors of the user.