I’ve also gone to Bing Webmaster Tools and tried inspecting url of one of my pages that is treated as a Soft 404 on Google. Here’s Bing’s console’s screenshot- https://ibb.co/sH28Qh5
There must be sth blocking search engines from indexing my pages
Hello,
Thank you for contacting Rank Math support, and sorry for any inconvenience that might have been caused due to that.
The www variation of your sitemap is currently returning an “Unauthorized Access” error page as you can see in my screenshot below:

You may need to check with your hosting provider to whitelist your sitemap pages in their firewall services. Kindly contact them.
After doing so, please ensure that all 4 variations of your sitemap page are redirecting to a final variation:

Please follow this guide and redirect to a final variation:
https://rankmath.com/kb/couldnt-fetch-error-google-search-console/#num-5-4-redirect-all-three-other-versions-to-your-preferred-variation
Once done, clear your website cache and try submitting your sitemap to your Google Search Console again. See if this resolves the issue.
We are looking forward to hearing an update from you. Thank you.
Thank you, I’ve contacted my hosting and will follow your recommendations. I will update you asap
UPDATE: Namecheap says they have fixed it and I have cleared site cache. As of now, the sitemap has been accepted by Google. However, one variation (the most important one since it has all my posts) is still getting rejected- https://ibb.co/1LVD1MG
Kindly advise
Hello,
After resubmitting the sitemap, you need to wait for Google to recrawl the sitemap.
Let us know how it goes.
We are here to assist you.
Hello,
Since we did not hear back from you for 15 days, we are assuming that you found the solution. We are closing this support ticket.
If you still need assistance or any other help, please feel free to open a new support ticket, and we will be more than happy to assist.
Thank you.