Writable PDF Portfolio not working on iPad

I have combined multiple writable PDF documents into a Portfolio. It works fine on a laptop or desktop with Adobe reader. However, when I open it on an iPad (with Adobe Reader and the latest IOS.), it comes up as ‘read only’.

I have tried making it Reader Enabled, but it also does not work.

I can fill in a standard writable PDF on an iPad, just not when that document is in a PDF Portfolio.

Can anyone please assist me in getting this to work?