I have an identical build at home with pihole and pivpn (wireguard) fully operational.
I did the same build and exact same steps at another location. Pihole seems to be working on the network using a PC/mobile device but pivpn won't work after connecting to wireguard. I get no internet connection and it times out. I'm not sure if i messed up somewhere or the ISP blocking it. It's a different modem to mine but I definitely did follow the guide to do port forward.
Thank you. I'll contact them for further assistance.
I might bring the unit back here and edit some of the pivpn/wireguard to my network and see if it works.