That happened to me once - I got very excited and made superium armour, then realised that it was the wrong tier. That said, the title is correct so I suspect they have made the right stuff.
Just to cover some obvious ones: are you double-tapping jump, as you would to go into creative flight? Also, if you know how, I'd double check the config for Mystical Agriculture as I believe there is a setting that allows creative flight - if that's been set to "false" for some reason, that might be an issue.
A bit more info about what pack you're using might also be useful; I had a quick look and found an issue that Avaritia was causing back in June - it may be completely irrelevant, but I thought I should mention it.
In the new versions, you are required to use the Flight Augment in the Tinkering Table. Augments can be used only on equal or lesser tier armor and tools.
Just figured it out today in ATM4, hope this helps.