Hi Cameron Jensen,
I have tested to created a list in a communication site and created a list in it.
Then I access the list in SharePoint application on an iPhone and I can see a "+" icon in the up right corner beside the search icon.
When I click the "+" icon, a window pops up in the bottom and I can click the "Add new list " to create a new item.
To better understand your situation and provide help for you, I would like to confirm some information with you:
- Could you please capture a screenshot of the list page on your iPhone?
- What is the version of your SharePoint iOS application? Please update to the latest version 3.18.0 (20180730).
- What did your list consist of? For example, I just create a list with some simple column type such as single line of text.
- What will happen if you create a new list and add new items in SharePoint application on your iPhone?
Does the issue only happen with lists in Communication Site? How about Team Site?
Best Regards,
Gloria