@tiagalho 

When you say connected via WiFi, are you connected to the Omada WiFi network you created?

If so its expected the VPN wont establish, the VPN is designed for connections coming from outside the Omada network (cellular as you say) or a neighbours WiFi etc..   When you are connected to the Omada network then you are not going over the router WAN port, therefore you wont establish the VPN

  @Philbert thanks for the response. I can't connect to my vpn even using other wifi networks outside home 

  @tiagalho 

Can you tell us what hardware you have running on the network?

Are you using an ISP Router in between the Omada Router and the WAN link?    If so have you enabled port forwarding on the ISP Router?    Are you also using a ddns server?

What error are you getting?   Does OpenVPN work for you?

Any info you can provide would help greatly..

  @Philbert OpenVPN worked fine. My ER605 is in the DMZ of my ISP router. However, I connected to my friend wi-fi and was able to connect to my vpn without issue. Is it possible to block l2tp connection? I ask this because I have this issue on all wifi networks at my job.

The error I get says that VPN did not respond.

  @tiagalho 

Ah short answer YES

I can say with certainty that any decent setup business network would have this blocked, from a business point of view it would be a massive security risk to leave this open as you would have no control over what got sent across that VPN, you also couldn't guarantee the VPN is legit.

If its your workplace, then for sure they have it blocked 

  @Philbert That may be the issue, not a big deal.

Thanks for your help :)

tiagalho wrote

  I ask this because I have this issue on all wifi networks at my job.

The error I get says that VPN did not respond.

  @tiagalho try allowed ports, like tcp/443 and tcp/80, then it should work if protocol is not blocked. If protocol is blocked, run it over proxy/socks or some tunnel over again allowed ports, as example ssh tunel to your own notebook which would use own dns etc...

  @btx 

To play the devil's advocate, personally, I wouldn't be pushing too hard to get this working.  

Your employer likely has this blocked for a reason, trying to circumvent this could result in disciplinary actions.    Ultimately this depends on where you work, in a cafe or small business this might not be an issue, however in most businesses trying to push VPNs through their network without telling them first.. your feet wouldnt touch the floor on the way out..

Just saying, tread carefully with this one

  @Philbert Not gonna mess with this for sure. If needed I just disconnect for jobs wifi and use my mobile data.