I've been having issues where I'm unable to enter certain Global Events that 'suggest' types of Gear. The latest example is a Survival run in Antarctica on Mount Slaughter. The restrictions are "No Wingsuit + Thermal Protection" - no level restrictions. So I go with Moby as he has the Solar Panel, but it simply won't let me equip it. It says "Unavailable" when I go into 'View More' in the Gear tab. I can equip any other type of equipment except the damn Solar Panel. Is there a Minimum level that my character has to be or something? I'm not getting it.

For the example given, the solar panel is thermal protection.

There are know issues, for level specific events, that involve the purchase
of gear in the menu for the event. You can buy gear at the level but it
will not allow you to equip it, no workaround as of yet.

But this particular Event has no level specified.

If there is no level specified, that gear can't be used at all. Period.

If the event, in the box below the name, if it says NO, it means no for any gear listed there.
So the event you mentioned says "No Winsuit - Thermal Protection"
It means No Wingsuit - No Thermal Protection
That is why you could not equip the solar panel, A.K.A. Thermal Protection.

Ah ok, I took it as No Wingsuit but you can use Thermal Protection. Thanks for the help!