is this "real" tubeless or some sort of home-brew with a cut off tube ?
have you taken out the valve core and used a decent track pump ?
& LOADS of watery soap ?
(I don't put the jizz in at 1st, just soap – in case it goes badly & I abandon, or end up wearing the stuff due to a blowout). Tyre should still seat well enough with some effort at the pump, then I pump up hardish & leave for a while with the pump still attached to the valve. Even if it goes down later it should stay seated and you can remove the pump head and squirt jizz down the valve neck with a syringe before refitting valve & pumping up for good)
(I do have a compressor – Aldi, cheap but massive & very rarely used. I do use it for tyres because it's quick but I can "always" manage with a track pump)