Took me a while to dig out my old Sabre books from when I worked for Trans States, but this should be the same for Alaska as Image is just an interface into Sabre.

In Sabre, check-in is restricted once an agent using a GATE set designates the flight is in FINAL. Once this is done, only agents using a GATE set can issue boarding passes. Agents at the ticket counter are usually restricted to AIR sets, which cannot override the GATE sets, meaning that once a flight has been restricted, they cannot set it back to OPENCI to check in passengers.

The native Sabre command to reissue a boarding pass is essentially a check-in entry. Once the flight has been set to FINAL, agents using AIR sets cannot issue boarding passes, regardless if someone has previously checked in or not.

I would think that in this case Alaska restricts their ticket counters to AIR sets. Kiosks are either set up as AIR sets or their own software has an automatic cutoff time in their programing I would think.

In the case of the OP, there are no "magic keystrokes" unless the agent is using a GATE set. The only other option would be a direct call to the gate agent (or someone with a GATE set) and asking for a reopening of the flight.