Welcome to the forum, todoroff!
A “common” (as in every year or two) issue that has caused, first, muted sound, and eventually NO sound, in one of my Resound rechargeable aids is failure of the receiver in the ear. Receivers are easily replaced by an audiologist, who can test a suspect receiver to determine if it’s faulty and swap the bad one out for a good one if needed. The receiver may have to be ordered.
If it’s past the probably-three-year warranty, and if you don’t have access to an audiologist to service your aids–say you got them online etc.–it is also possible to DIY this. You can determine if it’s likely that the receiver is faulty (assuming it’s charged and powered up) by handing it to a friend or family member with normal hearing and asking them to cup it in their closed hand they hold up to their ear and listening for whistling/howling feedback noise. If no one with normal hearing detects feedback, chances are good that a failed receiver is your issue.
You can replace failed receivers by ordering them online (I’ve used eBay), but you must be very careful to match a receiver you see online with the same brand, model, left ear vs right ear, and size (shown at the end of the aid going into your ear, when you remove the dome). For example on my Resound aid, on that silver bar at the end of the wire with the dome removed, I see “2 MP C”. I would need to order that exact spec for my ReSound Quattro right ear, or left ear. Left and right ear receivers are not interchangeable! and if it isn’t an exact match on the specification such 2 MP C (yours may vary), don’t order it. It may not fit your ear as well as the old one, and the settings could be wrong. You can find instructions online from ReSound to install the new receiver, if they’re not included. There are also YouTube videos demonstrating it; it’s not hard to do. Generally you’re going to push a sharp object like a sewing needle into a small hole on the aid to release the old receiver and then pop the new receiver into place. You do not need an audiologist to update settings on the new receiver if the old receiver was set correctly; it should work the same as when the old receiver was operating, though there’s always a chance that you get another defective receiver online. You also may need to use a hair dryer to warm the wire and mold it into the same shape as the old wire for a good fit. If you’re not comfortable doing this, you should pay an audiologist to handle it.
OH… one more thing… you said No obstructions… you did try (yes?) replacing the wax guard? A wax guard needing replacement can cause this issue.