Solar Panels gone

[tikal]

Hi

I've upgraded my Solar Panels up to level 18 but now they've disappeared from the buildings list.

I demolished one level and it appeared on the buildings list again. Rebuilt to level 18 again but it's gone again.

Have I missed something in the rules or is this some sort of bug?

Many thanks.

[RoYaL]

It's a new rule. Their max level is 18.