Downloading roblox

Hi there!

Today I went to download roblox on my iPhone 6 but it won’t let me. I did the usual downloading process and then I asked my permission from my dads iPhone it went away and then started to load but then stopped and said “Get” again. My sister has it on her iPhone 6 and I’ve deleted a few other apps that had a lot of MG bites but it still won’t download. What should I try next?