Unable to fix low engine %

[sk0941]

In the GE variant I have about 15% of oil in both engines, but I'm bot able to service the engines. When ever I click "service engine" I get met with a prompt that says "unable to service engine with cover in place" or something along those lines.

The thing is that I don't have any engine covers in place, I don't even think there's an option to place any atm. So how would I go about restoring the amount of oil in the engines?