Some problems

True, I’ve having the same issue.
Any way to edit a theme manually to add in the missing structured data?
There was an issue submitted:
https://www.ads-software.com/support/topic/google-structured-data-error-1

If there is a reason (eg semantic markup of the page/theme) you can use several H1s. New HTML 5 sectioning system allows logical placement of several H1s, where each logical section can have one H1. Sections can be: body, navigation, article, sidebar, footer, etc. Please see the video under “SEO H1-H6: How Many Keywords Can I Use?” (guy in the video: Google software engineer Matt Cutts):

https://www.hobo-web.co.uk/headers/

With the advent of HTML5 the answer to this question has significantly changed in both SEO and technical regards. It’s now not only possible to have multiple <h1> level headings per webpage that will make sense to search engines, but in most cases it’s actually the recommended course.

https://webdesign.tutsplus.com/articles/the-truth-about-multiple-h1-tags-in-the-html5-era–webdesign-16824

This very poor rating is more of a disagreement with the HTML5 spec than the theme.