Having just coverted to tubeless I had an interesting experience I didnt use C02 or the garage compressor just my trusty track pump, I didnt even use that much soapy water.
The problems definately where with the tyres I was using I’m running a standard dual ply minion dhf up front which went on and pumped up likeit had a tube in it.
I then tried three different tyres on the rear a dualply swampthing (brand new) – no hope nothing was getting it to seal an old spesh Eskar, again no hope.
Went and got a 2bliss ready Eskar went on with no issues again pumped up like it had a tube in.
Go figure, saying that it was probably just dum luck on my part! What tyres are you using?