Are you sure ? Switch to UN-screw. Pull trigger all-the-way. Did it make any sounds at all ?
Switch to IN-screw. Pull trigger all-the-way. Did it make any ODD sounds at all ?
Switch to UN-screw. Carefully, rotate the chuck as you slowly pull the trigger. Any sounds at all ?
Try switching it ''while its running''. Any clicking sounds ?
We presume you have tried slam / bang / and other 4-letter words.
No sounds? OK, you're right. Its dead.
First try the hair-blow-dryer trick, where you blow-dry hot, hot. Repeat the above steps when its hot, hot.
( The trigger-switches are VERY sensitive to water and dirt).
Still nothing ? I'm afraid it must be dis-assembled. Web search for the replacement-parts diagram.
(One picture = 1000 words). You'll need a multi-meter to test the battery-trigger-F+R-motor connections.
If the motor/gear mechanism is bad, bury it. Its value is 0.
Electrical problems are simple to fix. Trigger switches can be cleaned. Follow the diagram to re-assemble.
Hope this helps.