We have some very thin cracks above and below some of the windows in our house (1980s). Tried to fill one a few weeks ago and then painted one coat so far but the crack has reappeared - see photo.
Looks like a crack between two plasterboard boards.
Suggest you have a look at the foot of this page, lots of answers about this problem, or use the search function at the top right search fro plasterboard crack filling or such?
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local