There is either food debris blocking the action of the dispenser lid, or the solenoid which releases the door is sometimes failing to operate. The latter fault can be due to either a faulty solenoid or a loose/damaged cable connection anywhere between the main board and the solenoid: bear in mind that every time the door opens and closes there's a flexible connector which gradually fatigues and there are electrical connections which can be loosened if the door is regularly allowed to slam shut.

Your machine is still in current production, so it may still be under the manufacturer's warranty. if so, then repairs will be free provided the fault is not due to a failure to follow the operating instructions.

It's not really a DIY fix unless you are a competent and experienced home appliance repairer, but you can check for any food debris around the dispenser lid. If in any doubt run the machine empty using dishwasher cleaner. The possible electrical faults I've mentioned aren't necessarily expensive in terms of parts, but the labour will typically be about one hour.

An alternative is to use the new detergent dispenser from Finish. This sits in your machine, preloaded with twelve doses of detergent which are automatically released with every wash. It's an expensive way to buy dishwasher detergent, but it's a quick and relatively cheap fix which may buy you time until you can afford a proper repair.

If you do think that you may be able to diagnose and repair the fault on a DIY basis then I highly recommend the Haynes Dishwasher Repair Manual which you can either buy or perhaps borrow from a public library.

I'm hope that you have found my reply to be of use, all that I ask in return is that you take a moment to rate my answer.