I dont know if this will work for you, but it could be because of corrupted files
before doing this try reinstalling roblox studio though
Go to finder, Library/Roblox and open the latest folder(it’ll have some long name)
Then spot (GlobalSettings_13.xml) and (ClientSettings) and delete them, these files contain studio setting which could be malfunctioning
Restart Roblox studio
Let me know if it works
Try checking your IOS version (10.11 should work)
if its up to date, then try running roblox studio in “safe mode” (hold shift key during startup) if it works in safe mode, there’s likely a conflicting background application causing the issue
You can also check the crash reports, see if that tells you anything, otherwise you’ll have to contact roblox support