60psi may wreck the rim, there is usually a max of around 40 for tubeless MTB.
Take off all the tape, and clean the inside of the rim with meths really well.
Get some normal electrical tape, and use that. Apply it so it is stretched on, and only a couple of times round.
Put an X shaped cut on the valve hole.
Put a tyre on with a tube in it, and inflate. Leave for 24 hours, or even go for a ride.
Take tube out, being careful only to unseat one side of the tyre. Put tubeless valve in. Add soapy water with fingers to the unseated side of the rim. Carefully pull the unseated side of the tyre toward the rim as much as you can. Make sure not to unseat the other side.
Inflate until tyre seats (should be max 40psi).
See how long it stays up. Anything over a minute is not bad, go ahead and inject Stans. Anything less than a minute, maybe there are other problems. Where is the air coming out from?