I have found the problem is with iCloud. I contacted Apple and (48 minutes later) the told me I had to import photos directly from the file source, not iCloud. I have just used the Affinity App connected directly to my camera and it works fine. It reads nef files. All my photos are backed up on an external hard drive but the iPad won't access as it can't power it up. It also can't read nef (raw) files from a SD card. So, apologies, but the problem I have is with the Apple iPad and not Affinity.
However, if anyone on this forum has a solution, I would appreciate some help. I can't store all my raw photos (1000's) on SD cards and plug them into my camera everytime I want to access and edit them.