Heat tape barely heating?

I made two new snake racks and am using 6" THG heat tape. I use this with my other snake rack and hatchling rack and temperatures are fine but the two new snake racks will not go higher then 77.7F even without a thermostat. I have new snakes coming in tomorrow and I have no clue what is going on.

My first snake rack is 6ft tall and so is the heat tape. These two new cages are only 3ft tall and again so is the heat tape. Could this have something to do with it? How can get the heat to go up?

How did you connect your power cable?

I use ring terminals and eyelets. It is what I have always used.

Make sure you have a good connection.

I picked up more 6" heat tape and added it to the other heat tape to make 12". It is working now. Temperatures are up to 90F with the thermostat.