How to turn this off [[maybe_unused]]

In a class after adding a 5th method to a public: it requires this 

[[maybe_unused]]

What is this and how can it be shut off, I am not aware of any limits on the number of public methods. The code cannot be posted, sorry about that. This issue was discovered after the project was started.

Update:

My apologies for posting, the issue has been resolved. It was a scope issue that compiled and linked without any errors before adding the additional method. Corrected that and it is now working. Unsure how that actual problem was overlooked.