My Asus RT-AC88U is running AsusWRT-Merlin firmware version 386.9. This version allows me to use IPVANISH with no problem.
When I upgraded to any newer version of AsuWR-Merlin especially the latest version 386.12_4, I cannot run IPVANISH on my RT-AC88U.
I reset my RT-AC88U to factory settings after flashing the firmware with no luck. The only version that seems to work is is 386.9.
If anyone had a similar problem, please share with me how you solved this issue.