I havent opened Loopy for a month or so.
It now says "Loopy HD" Beta Has Expired.
Testflight says Loopy HD Unavailable.
Is it safe to delete the app and reinstall from app store?
I dont want to lose any data
That's right, alas the TestFlight betas expire. I'd use iTunes or iExplorer to back up your Documents folder from Loopy, then install from App Store (but don't delete first - that should hopefully preserve your data, but I can't be 100% sure; it's flaky like that).
Ah ok thanks