Together with your router manual you might follow up if this is an exact match with your device.
On your phone go to Settings > Network and internet > Internet > Select your Wi-Fi service provider.
Here you will find Network details (you probably already did this) but there are a number of things that may or may not be a fit with your router, so you might write down all those details from the phone and check they are either an exact match with the router report, or are part of the router “way of doing things”.
Some further details which you could change on your phone are revealed after you “Forget the network” now under Advanced options before you re-enter password.
One variable to check with your router manual is does the router offer DHPC or static. As long as you remember what you changed you can experiment with changing this before you enter password, to see if it changes anything.
According to published builds https://images.ecloud.global/stable/starlte/ you are not even on latest Android 8 (Oreo), there was an e-0.20-o-20220118158074-stable-starlte and then being a stable build you should have been offered an OTA Android version upgrade.
So I think it would be worth checking out this suggestion
Issues with the Updater and a solution.
if only to check what changes … 
@Manoj, please could you clarify, when an OTA upgrade (from quite a long time ago) is marked “completed” does this mean that the OTA service itself is no longer available? Thanks.