I believe there are a number of posts on this for the PC/mobile version.
4 Star Kingdoms do NOT give +50 Gold like they are supposed to on CONSOLE.
“This Kingdom” Pre upgrade:
Base +20,Quests +25, Kingdom Power +100
"This Kingdom " 4 Gold star Post Upgrade:
Base +20,Quests +25, Kingdom Power +100
Income total Gold per day is identical as well.
This is why I stopped leveling Kingdoms at 3* (for now), we need 9 Troops (and all 9 to count, looking at you Zhul’Kari 
) in a Kingdom to realistically get it to 5*.
The Holy city will be blaring its trumpets real soon…
First I’ve heard of this. You mean that the income DOES increase at silver star and 2 star, but NOT at 4 star?
Have you restarted your game? It seems really weird to me that it wouldn’t work in just one case.
How about the 5-star bonus?
1 Star (Silver) +50 OK
1 Star Gold Double Tribute Reward OK
2 Star Gold +50 Ok
3 Star Gold Double Chance OK? ha
4 Star Gold +50 per Day BROKEN
You only get +145 when getting to 4 Gold this is identical to 2 Gold Stars. the Reward for 4* power does not apply/work
its one that @Sirrian - said would be fixed for pc starting this week but cosmetically wouldnt be fixed until 2.1.
sorry - not sure if it is fixed for consoles since its server side?