If drum spins and clothes stay cold, heating element is usually burnt. Easy multimeter test, replacement available.
See if any of these signs match your device — each one increases the likelihood of this fault.
These are the causes we encounter while repairing Dryer spinning but no heat — ranked from most to least common.
Burnt heating element (most common)
Burnt thermal fuse (overheating protection)
Bad thermostat
High-limit thermostat shutting off heat
Disconnected element wiring
Bad control board
Any of the following = a danger signal — call now and don't try to fix it yourself.
On-site diagnosis, clear pricing before any work, and a documented 6-month warranty.