We have an app (WeSupply Labs) on our site that generates an estimated delivery date on our product page. The problem we are having is when we have the Cloudflare proxy status for CNAME www set to “Proxied”, the app will not work and generate a date (gives date not available error). The app is making entries in our logs with every page load request:
ERROR: WeSupply response error with status 503
ERROR: No response from WeSupply
If we change the proxy status for CNAME www to “DNS only”, the app works correctly and a date is generated and no 503 errors in logs.
The app will sometimes work even with CNAME www set to “Proxied” but only if we access site through a VPN. We have tried accessing with multiple different local IP’s from our ISP’s, but no luck.
Any idea on what can be causing this? Do we have to whitelist the app IP somewhere in Cloudflare?
Any help would be greatly appreciated!
I did a quick search 
for error 503 #CommunityTip, https://community.cloudflare.com/search?q=error%20503%20%23CommunityTip%20%20 and found the 503 CommunityTip.
An “Error 503: Service Unavailable” with no Cloudflare in the message means you need to contact your hosting provider for assistance. It generally means your host is rate limiting requests to your site or that I’m Under Attack Mode has been enabled on the domain.
A “Error 503: Service Temporarily Unavailable” with “Cloudflare” means you are hitting a connection limit in a Cloudflare data center. When this happens, please contact Cloudflare Customer Support. Include as many of the details mentioned in the Quick Fix Ideas as possible.
Thank you, but I don’t think my host is the issue. We are only getting the 503 error in logs when Cloudflare is enabled and when accessing site from certain IP’s.