I apologise in advance for the fact that I am essentially a layperson with minimal networking knowledge. Hoping someone might be able to offer some suggestions re the following issue:
New HP Chromebook 14 connected to vigor 2830 and to internet without any issues initially out of the box, updated chrome OS and some apps, all seemed fine. Came to use it again a few days later and it is connected to the Draytec's WiFi network but has no internet access. Other devices are connected to the same router and can connect to the internet without issue. The Chromebook will connect to the internet fine via the hotspot on my phone (with cellular mobile switched off so presumably is accessing the internet through the phone's connection to the draytec router).
The router is set up with the static IP provided by my ISP and has been working fine otherwise. When I run connection diagnostics on the chromebook, after a short while it just says: captive portal "cancelled", DNS "failed", Firewall "cancelled" and a few other things that escape memory but essentially everything is failed or cancelled. On the chromebook's WiFi network info it says the IPV6 address is loading and never loads but this happens on the hotspot too so I assume it is not the issue. IP address on the chromebook is set to configure automatically. I dare say there are numerous settings on the router which would be helpful for any potential troubleshooting so please let me know what settings if any I should report back to you. The router firmware was updated a few months ago so shouldn't be far out of date. Any assistance will be very gratefully received.

Do you other devices connect over IP v4 or v6?

Does the Chromebook report a valid IP v4 address when it connects to Wifi, and show the router with as the default gateway?

I've had this problem with a ChromeBook from new. I've finally found a solution today, although not sure if it's a long-term solution.

Symptoms:
The ChromeBook connects to a 2920 over 2.4Ghz Wifi, receives an IP address, but can't ping any other machines on the local network or internet access.
The ChromeBook connected to the 2920 over wired ethernet works perfectly.
The ChromeBook connected to a separate non-DrayTek 5Ghz WiFi AP with a wired connection to the 2920 works perfectly.
My local network is set-up with a 192.168.2.* range rather than the default 192.168.1.* range (that's another story...). The router is thus 192.168.2.1. The ChromeBook had been allocated 192.168.2.15

Using the Crosh limited shell on the ChromeBook, I eventually isolated that the routing table only had one entry for the local network:
192.168.2.0 0.0.0.0 255.255.255.0 U 0 0 0 wlan0
I.e. There's no default entry and no entries with the router IP.
Somehow during DHCP negotiation (I think that's when the table is set-up), the correct routing set-up fails. Perhaps DrayTek and Google's implementations of the protocol interpret something differently.

I fixed it on the 2920 by adding a static route and enabling it. This made the ChromeBook work. But the strange thing is that when I then disabled that static route in the 2920, the ChromeBook continues to work, including after changing APs and then back to the 2920, so I presume that some table is now set-up correctly. I also statically allocated the IP address in the 2920. Another strange behaviour is that I had to do this enable/disable fix on the 2920 for each user logged into the ChromeBook.

Let's see if my fix continues to work over the next few days...