I've been wondering a lot about this when it happened which I was using
Walli* app yet after I have changed my ROM, maybe the app gets blank no matter how I install it. But after a time, I've also realized that there is another app called
Reface with the same problem in which I can't use them because they're blank like there is no connection to the Internet.
Note: I'm using Cloudflare Family DNS on my router and Firewall settings such SPI and DOS protection.
7.1.2 Android custom ROM