On clicking the shortcut or using the hotkey, I get this fun error:

The mod Solar Calculator (0.3.11) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event solar-calc::kaktusbot-sc-switch-calc-gui-input (ID 240)
solar-calc/control.lua:32: attempt to index local 'main_gui' (a nil value)
stack traceback:
solar-calc/control.lua:32: in function 'switch_gui'
solar-calc/control.lua:178: in function
<solar-calc/control.lua:176>

I have a few mods that add to the GUI, so I will be going through them to see what causes this exact issue, updates will (hopefully) come shortly.

That means that on_player_created event wasn't fired or game.players[] didn't contain you while script.on_init was initially run.
I had similar bug for a really long time, I've seen people complain at it on Space Exploration Discord server, even here https://mods.factorio.com/mod/solar-calc/discussion/6251834a9fbedb9839f34008
But I have no idea how it can be happening.
I've started complete rewrite of the mod 6 months ago but dropped it soon, because I didn't like my new UI.
So I will not update my mod anymore until I get it together and finish a rewrite.