Thanks Anke. I know that the makefullpath is not working for ios (hence the problem). I was hoping there might be an alternative. Just for context, I spent some time working out the details for posting a file using the android build a couple of years ago. It came down to first finding the full path for the postfile block. So, I have the same problem now with ios until the path can be determined on the fly. Here is a link to the previous post showing how finding the full path was critical to posting the file in android:
Looking for help posting a csv file to a php script (for insertion into mySQL table) using postfile block (not posttext) - #16 by Mark30289