I use smelly tabs occasionally when we get a little stink. Generally only happens when parked for a week or so with 4 people contributing to the black tank. It’s inevitable if there’s a lot of solids being deposited and not dumped before getting near full. Or worse if ya gotta drive a distance with a full black tank.
If that is the case with your new rv either the vent isn’t working or you haven’t flushed out any poo in 2 weeks. (Still seems like a stretch with 1 person, 2 weeks unless you poop like a horse…lol).
But you’re just throwing money down the toilet since you appear to have an issue and the issue isn’t from a massive collection of waste in your tank.
This will continue to be difficult if you continue to ignore sage advice and continue to hood for magic fixes.
Dip the tank (unless you have the oddball scenario posted above with an offset pipe, which you presumably would have seen even with poor vision…)
Depending what you find, do what I said and go make the contents easier to dump by agitation. Go for a drive if you can’t solve it other wise.