First, as Andrew suggests, make sure you're not out of exposure range in in auto (the needle should point to a f-stop value). Then try it in manual mode to see if the shutter works. If it works in manual mode, check your battery and battery contacts. If you're using a zinc air battery, they will degrade over time even if not used; though probably not in a week. If you don't have a cap on the lens, your meter is on and the battery is being discharged.
If the problem is power to the meter for auto exposure, and the battery and contacts are ok, then it may be a bad electrical connection inside the camera. This would be consistent with an intermittent problem. Opening the back should not have any impact. It could be coincidence . But it may be that it the process of opening and closing restores (temporarily) the connection.
Also, if your repair person simply "loosened" the crud in the shutter with lighter fluid or something similar, the shutter can work for a while and then stick again. But that would effect both auto and manual modes.