DNS Over TLS Doesn't Work on Android Pie

i also have the same problem. I was able to get DoT to work initially and it stopped.
https://1.1.1.1/help#eyJpc0NmIjoiWWVzIiwiaXNEb3QiOiJObyIsImlzRG9oIjoiTm8iLCJyZXNvbHZlcklwLTEuMS4xLjEiOiJZZXMiLCJyZXNvbHZlcklwLTEuMC4wLjEiOiJZZXMiLCJyZXNvbHZlcklwLTI2MDY6NDcwMDo0NzAwOjoxMTExIjoiTm8iLCJyZXNvbHZlcklwLTI2MDY6NDcwMDo0NzAwOjoxMDAxIjoiTm8iLCJkYXRhY2VudGVyTG9jYXRpb24iOiJZWVoiLCJpc3BOYW1lIjoiQ2xvdWRmbGFyZSIsImlzcEFzbiI6IjEzMzM1In0

Port 853 is available for both Cloudflare domains one.one.one.one and 1dot1dot1dot1.cloudflare-dns.com. DNS is set for 1.1.1.1.

but in my case it does not work for mobile Telus or my ISP network.