It is geting too late to get out the calculator. That resistance equals about thirty watts output from the heating element I think at 120 volts into the element. If this is enough for chair heat is unknown to me.

Another test is to see if there is 120volts at the element connections when the unit is on. If there is and still no noticeable heating the resistance of the element has gone too high.

There is a chance it is a variable heat unit and the output to the element is too low voltagewise and the defect is in the control circuit. I have no real knowledge about these type of chairs. Just replied as no one else with more knowledge did. They may yet.