InselAir made this announcement:

First on February 10:

Since Sunday afternoon February 2, Insel has been experiencing operational issues with its Fokker aircraft. Although the Fokker aircraft is airworthy, issues were identified during an audit done in cooperation with the Department of Transportation (CCAA). Last Saturday, it was decided by InselAir, due to the uncertainties surrounding the operations, it was best to postpone the operation of its Fokker aircraft until further notice.

Later on February 11 it updated the situation:

Unfortunately at the moment booking a ticket through our Website or any other Sales channel is not possible until further notice.

Please keep in mind that passengers who have already booked a ticket to and from St.Maarten are protected on the Corendon Dutch Airlines flight.

We are very sorry for this inconvenience.