I bought lifetime on iOS a few months ago and I was able to use some of the pro features. However I stopped and recently logged in to see all the pro features greyed out.
I might have already helped you via email. If not, make sure you are signing into the same account. 99% (if not 100%) of the time, a user will sign back in after awhile, and sign in using the wrong email address. If you can find your original "welcome to renshuu" email, you can see what it was sent to.
If not, you can send me (via the ? button at the top of the app) a screenshot of your order receipt, and that can help me find your original account.
