3. ATM can't take anymore cash at present.
AFAIK, electrum doesn't have a limit (well... Theoretically, there'll always be a limit, since electrum is written in python, the maximum value of a float variable is 1.7976931348623157e+308*). ...
Addresses don't have a limit (well... Theoretically, i guess one address can only be funded with a little less than 21.000.000 BTC)...
The only real "limit" is probably imposed by the ATM vendor.
Either his software is buggy, or his ATM is broken, or his ATM software has built-in checks that stopped you from purchasing BTC.
At any rate, this isn't an electrum problem... You'll have to contact the ATM's customer support to get this one sorted out.
Good luck!
*https://stackoverflow.com/questions/3477283/what-is-the-maximum-float-in-python