I've got an award booking MEX-CUN-SJO with AM690 in January. The last few weeks AM690/AM691 have shown plenty of availability on all dates in January and so I wanted to change dates recently. However, for some reason ALL availability in ALL booking classes has been zeroed out between 7 Jan and 28 Feb on these flights.

Does anyone know why this is? Is this common practice by AM? Can I expect availability to return or does this mean the flights are cancelled?

Thankful for any insight