I have made much more simple sites like this, but they were indexed just fine. I have tried adding backlinks as well. Could there be any other issue here?

thanks for sharing good Information.

In your https://gro-usa.com/page-sitemap.xml are 2 links. Your https://gro-usa.com/post-sitemap.xml is empty. Add more informative, high-quality content for you visitors....

Yes, the website is in maintenance mode, though this is a recent thing that I implemented. This is absolutely not the cause of the issue. I have taken maintenance mode of...

Your website is in maintenance mode

There's a tweet about your issue from John Mu. https://twitter.com/JohnMu/status/1387874087045844996?s=20 Unfortunately there's a bug there in Search Console. When we we...

Content outreach and social media is the best way to get rank and traffic as well .

When you submit a site map it indexed all the pages of your website but it will not index the pages which are not allowed to index e.g they are disallow in robot.txt file...

Covid 19 did not hit the ranking directly , but few updates which came from google in these days are effecting the ranking .

Why not use Google reviews?