I have been struggling with the custom background option. When I use it the proficiencies (tools/languages/skills) do not get updated. I access the site via iPhone. This is repeatable every time I create a new character. I can modify older characters with the custom background and the proficiencies update as expected.

Yes it does, it just takes a while. Give it an hour and check again.

I will try this. but if even if this is true it needs to be fixed to update immediately like it used to/how everything else works 

I agree.

I did work for me after waiting a bit

Same problem -- super annoying.

Same problem.  They've only had 4 years to fix it, so everyone be patient.  I'm sure a fix is coming...