Not sure what could be causing this. I made a Jetpack and was messing around with it, I hit the hotkey to change the modes, and it Disabled it fine, but when I hit the hotkey again to Enable it won't do it. It's just stuck on Disabled and I can't do anything about it outside of crafting an entirely new jetpack and not hitting the armor mode change button. I made sure to assign a hotkey for armor switch mode to a key that is completely free and it's still giving me this problem.

1.10.2 mc version with the latest Mekanism build.

Edit: I should mention that I also hear the sound properly when I hit the armor switch key, and continue to hear it despite the Jetpack being stuck in Disabled and not enabling.

Are you playing on hermitpack because ive had the same issue

I am not, I'm playing on my own Forge server with mods I handpicked myself.

Experienced this issue on FTB Infinity Lite for 1.10 v1.0.1 Keybinding in pack was set to Shift-F. After eliminating conflicting keybinds the issue persisted. Changing keybind from Shift-F to F without a modifier fixed the issue for me.