In the CotEditor app 
on your Mac, choose Format > Reset Syntax Analysis.
If syntax highlighting doesn’t look correct, first try the following:
In the CotEditor app on your Mac, choose Format > Reset Syntax Analysis.
If it doesn’t help, the possible causes include the following:
There is an issue in the text itself, such as invalid programming syntax.
There is an issue in the syntax definition.
CotEditor’s syntax analysis cannot determine that part correctly.
If the syntax is correct but the text is still not highlighted as expected, please report it to the development team. For contact information, see If you can’t find a solution.