So I'm ridiculously high and can't figure this out. I just got the Grasscity app and it seems fine and all but when I go to post something is says I don't have permission. Idk if it matters but I'm using an iPhone 6s iOS 10.1
You'll be told to clear your cache first. If that doesn't work, come back and let us know and we'll tag the tech person. (That way we can already say that you have cleared your cache and go from there.)
I prefer the mobile browser over the app. The app is hard on my battery plus I just prefer the mobile browser. I only use Android but I would think it works the same. Go to Applications in Settings and find the App and then go into the Storage part of the app and clear the cache. Maybe someone with an iPhone can better direct you.