Something is not right, it would take much colder temps than just 30's to lock it up.
I'm now wondering if something else is not playing a role in what's going on?
Most likely the PTO engagement killing the engine is probably a interlock issue, or an electrical issue, or possibly from the lack of hydraulic flow, disregard it right now.
Something either got damaged or disconnected when the tractor was moved, as the only other real option is it is actually cold enough to have frozen, which would mean that the transmission and rear end is full of water (Very ODD).
If you find no hydraulic connections that were disconnected when it was loaded, like via a tie down strap or chain, drain the Hydraulic fluid and check for water.
Only other explanation is that the hydraulic pump or drive has gone out, again very rare!
One move would be to loosen the output line from the pump and see if there is any flow from the pump.