AC doesn't want to take a charge

AC hasn't been used for a few years, as charge slowly leaked out.
When I started work on it and pushed in one of the charge valves there was a little burst of air, so it did hold something.
I removed the condenser and had it cleaned and tested at radiator shop. OK.
Put in new receiver-dryer.
Put new valve cores in high and low ports.
Put new R-D to POA hose as original was frozen to R-D fitting and broke.
I disconnected super-heat wire.

Put vacuum pump on system and it pulled to about 25". When I closed valves, it held the vacuum for at least 30 minutes.

I have several old stock drums of R12 Freon, so I am recharging with that.

Work being done at about 75 degrees outside temp.

After closing valves to gauge set, I attached Freon. Opened and cleared line.
Then opened low pressure valve (going to POA) to charge.

Low pressure gauge jumped to about 85 psi.

Started engine, turned AC on, temp to cool, fan on high.

Drum was sitting on scale to watch charge.

After 10 or 15 minutes, there still was no change in weight, or change in discharge temp.

Briefly, closed low valve and opened high side to try that. Gauge also went to about 80 psi. Didn't make any difference.

Compressor clutch is engaged, and you can hear compressor working. Sounds normal.

Tried another 10 or 15 minutes on low side. Still nothing.

Disconnected everything. I thought maybe new valve cores weren't opening, but when I pushed in pin there was a discharge under pressure, so I think they are working.

What might be the problem?

Thanks