Homes are no longer requesting an upgrade.

My homes have reached level 4 and no longer request an upgrade.   I was on level 10 and had 17 homes.   My people were at 100% happiness.   My services are at full capacity and I am serving more than my homes need.  Nothing has happened for several days.  I have read thru several threads and saw that possibly adding new homes would help the situation.   I have since added 5 new homes and they also get stuck at level 4.   I don’t know what else to do.   It is becoming extremely difficult earning money now.