Just thought I would share with the community a common problem that a lot of my clients have been experiencing lately and a new troubleshooting solution I have discovered.
If you are getting the error code within their banking screen showing:

Then ensure that you have ‘Background app refresh’ on. To get to this go into Settings> General> Background App Refresh. I would recommend turning it off and then back on again”

I hope this helps anyone experiencing the issue!
Emily