Hi Robert,
After you configured Dynamic VPN in SRX240H, you were no longer able to use the J-Web(GUI) on this device. Am I right? Please correct me if I'm wrong.
If above is your case, then it is an expected behaviour. Both Dynamic VPN and J-Web uses port 443 which is HTTPS. So, if you would like to access J-Web on the same 443 port, you gotta use something like this - set system services web-management management-url /mgmt
Use can use "/mgmt" or "/admin" or whatever suffix you want. Now when you access the J-Web via browser, you need to enter - https://192.168.2.1/mgmt
For more information, please refer to the following KB article - https://kb.juniper.net/InfoCenter/index?page=content&id=KB33505
Alternatively, you can also use J-Web to listen on a different port if you don't want to use the above method.
e.g.:
set system services web-management https system-generated-certificate
set system services web-management https interface ge-0/0/0.0 port 8443