It means your website is not working properly. can you start it locally?

you can access the direct url without cloudflare (hint: you might want to hide your url), check with Optimizely support service for that. once you obtain the exception (from that url, or from the log), you will hopefully figure out what's wrong 

This works fine on my LOCAL...I checked with Optimizely, and they said

There is no option to bypass Cloudflare.
 
The error from Cloudflare is showing that the web app is not responding within the timeout window. Bypassing Cloudflare's timeout will only sit at the loading screen for even longer until the browser gives up.

I cannot figure out what the error from the logs is or what's causing the time out.

All I did was upgraded following Nuget packages

EPiServer.CMS.12.20.0 -> EPiServer.CMS.12.22.2

EPiServer.CMS.AspNetCore.12.15.0 -> EPiServer.CMS.AspNetCore.12.16.0

EPiServer.CMS.AspNetCore.HtmlHelpers.12.15.0 -> EPiServer.CMS.AspNetCore.HtmlHelpers.12.16.0

EPiServer.CMS.AspNetCore.Mvc.12.15.0 -> EPiServer.CMS.AspNetCore.Mvc.12.16.0

EPiServer.CMS.AspNetCore.Routing.12.15.0 -> EPiServer.CMS.AspNetCore.Routing.12.16.0

EPiServer.CMS.AspNetCore.TagHelpers.12.15.0 -> EPiServer.CMS.AspNetCore.TagHelpers.12.16.0

EPiServer.CMS.AspNetCore.Templating.12.15.0 -> EPiServer.CMS.AspNetCore.Templating.12.16.0

EPiServer.CMS.Core.12.15.0 -> EPiServer.CMS.Core.12.16.0

EPiServer.CMS.TinyMce.4.3.0 -> EPiServer.CMS.TinyMce.4.4.1

EPiServer.CMS.UI.12.20.0 -> EPiServer.CMS.UI.12.22.2

EPiServer.CMS.UI.Admin.12.20.0 -> EPiServer.CMS.UI.Admin.12.22.2

EPiServer.CMS.UI.AspNetIdentity.12.20.0 -> EPiServer.CMS.UI.AspNetIdentity.12.22.2

EPiServer.CMS.UI.Core.12.20.0 -> EPiServer.CMS.UI.Core.12.22.2

EPiServer.CMS.UI.Settings.12.20.0 -> EPiServer.CMS.UI.Settings.12.22.2

EPiServer.CMS.UI.Sources.12.20.0 -> EPiServer.CMS.UI.Sources.12.22.2

EPiServer.CMS.UI.VisitorGroups.12.20.0 -> EPiServer.CMS.UI.VisitorGroups.12.22.2

EPiServer.Find.15.0.3 -> EPiServer.Find.15.1.1

EPiServer.Find.Cms.15.0.3 -> EPiServer.Find.Cms.15.1.1

EPiServer.Find.Framework.15.0.3 -> EPiServer.Find.Framework.15.1.1

EPiServer.Forms.5.5.1 -> EPiServer.Forms.5.6.0

EPiServer.Forms.Core.5.5.1 -> EPiServer.Forms.Core.5.6.0

EPiServer.Forms.UI.5.5.1 -> EPiServer.Forms.UI.5.6.0

EPiServer.Framework.12.15.0 -> EPiServer.Framework.12.16.0

EPiServer.Framework.AspNetCore.12.15.0 -> EPiServer.Framework.AspNetCore.12.16.0

EPiServer.Hosting.12.15.0 -> EPiServer.Hosting.12.16.0

Geta.NotFoundHandler.5.0.6 -> Geta.NotFoundHandler.5.0.7

Geta.NotFoundHandler.Admin.5.0.6 -> Geta.NotFoundHandler.Admin.5.0.7

Geta.NotFoundHandler.Optimizely.5.0.6 -> Geta.NotFoundHandler.Optimizely.5.0.7

Geta.Optimizely.Sitemaps.3.1.0 -> Geta.Optimizely.Sitemaps.3.1.1

How can I troubleshoot to figure out the issue?

Thanks

Daman

Issue has been resolved by updating to latest Episerver Nuget packages