Two stories both true First the one I hand a hand in.
Toilet would not drain indicating tank full. only it was not it was empty
Toilet down pipe was clogged.
And now the other one Same symptom as you
Well he finally got the tank empty (He did not say how) and investigated.
Turns out the builder when they cut the hole in the floor to install the toilet down pipe rather than toss the half moon cuts in the nearby trash. Just dropped them into the tank... They were returned to the company CEO.
Now.. if you are sure it's not the toilet.... A "Porta Potty" service can suck out the tank. Then it might be possible to inspect with an endoscope (you can get 'em that plug into your cell phone)
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times