Thanks for the update.
I tried looking for your theme to install it and help you address this problem. Unfortunately, it seems the Inova theme is a commercial (ie paid) theme. Commercial theme authors do not give WordPress support volunteers here access to their products, making it impossible for us to install the theme and provide any support.
Please get in touch with the author or marketplace where you purchased the theme from for assistance. They built/sold the theme, and are in the best position to help you out.
Good luck!
PS: In case you’re not convinced this is 100% a theme issue…
Here’s a blog post from one of the demos of the Ionova theme, and you can see it uses H2
for the post title/headline: https://droitthemes.com/wp/inova/products/duis-aute-irure-dolor-in-reprehenderit/
And here’s a blog post from WordPress’ default TwentyTwenty-One theme, but you can see this theme uses H1
for the post title/headline: https://2021.wordpress.net/2020/10/16/a-love-of-nature/