Hi and welcome.
I may have nothing of use for you as I don't use an Android/SmartPhone Device.
However, I will lay out how Secureline connects for me relative to how I use it on my laptop.
Secureline service is 'specifically' for use when connecting to "Unsecured WiFi Networks" as Internet Cafes, Airports etc. where no password/Network Key is required.
I never allow any Network to connect "automatically" from the list of Networks available even if I've used it before.....
When I boot up I will choose which network to connect to. If the network is "Unsecured" Avast Secureline ICON appears in the Tray and a popup appears stating the network in Unsecured and do I want to connect to Secureline: Yes or No.
If the network is Secured with a password/Key then ICON appears, However Secureline does not recognize the connection as 'Unsecure' so there is no Message to connect although one can connect manually at any time.
The Key here for me is that I chose to connect MANUALLY not Automatically, this seems to make a difference in how Secureline responds to connections for me.
Good luck.

Edit: Hopefully, someone who actually uses Secureline on Android can add.