If the office web apps url was https, make sure you have a correct certificate (that's not expired) to it. Use:
Set-OfficeWebAppsFarm -CertificateName "Certificate Friendly Name"
If you go to your event viewer on your office web apps server, it may contain more information on it. Should be a category called "Office Web Apps", also, check your Office Web Apps logs here: C:\ProgramData\Microsoft\OfficeWebApps\Data\Logs\ULS
May it be because of the SSLOffloaded set to true and there is no load balancer in front of it, as far as I know? Also, in the article I provided a link for it's said that I may want to rebuild the bindings. Does it seem like an issue that can be fixed rebuilding the bindings?
SSLOffloaded means the SSL cert is given from the firewall or netscaler that you have inbetween as the middle man to the client user upon navigating. If you have the SSL cert on the office web apps server in IIS -> Server Certificates, you probably aren't using SSL Offloading. Use Set-OfficeWebAppsFarm -SSLOffloading:$false on the farm. If the binding didn't work, you wouldn't be able to get to office web apps at all.
Do you have the externalurl set? type in get-officewebappsfarm and if there isn't an externalurl set, use this to set it: set-officewebappsfarm -ExternalUrl "https://<yourOWAUrl>"
Is the WOPIzone using external-https? Run on the SP server in powershell get-spwopizone, also can you paste in the farm settings in your question from get-officewebappsfarm from your OWA server?
in your internal url and exernalurl in the office web apps farm when you execute the command 'get-officewebappsfarm' it says officewebapps.contoso.com not https://officewebapps.contoso.comis that right?
Oh dear, I apologize. I see it. can you list your wopizone? if you go to your sharepoint server, open up sp management shell and type this in: get-spwopizone, what does it say?
:33057784, BTW, just to clarify by "access from external network" I mean accessing our LAN via Client VPN connection which on my computer has ip address from a network that is different that our LAN.