I use Opencart v3020 with Journal theme and php v7.3.
Our site is running from Cloudlare and have changed nameservers to Cloudflare.
All is running smooth and we have no error in Opencart error log.
The problem comes when installing the Nitro Cache.
After installation you get no error and nothing in error log.
You can see that pages loading faster and so on.
You can add a product to cart.
BUT when you go to checkout/checkout
You get "502 Bad Gateway" and under that you see "cloudflare"
I contacted the host and they say it is Nitro Cache creating the error but the Nitro Cache works if I disable the Cloudflare and load from host.
Have anyone seen or had this issue before?
I have tested almost everything so my brain is not in function anymore

If anyone knows how to fix it?
I can pay you if it helps....