IF your GPU is still under Warranty by MSI I suggest you open a MSI Warranty Ticket and see either if MSI will send you a new fan or RMA the GPU card to be checked and fan replaced.
Normally most GPU Manufacturer has a 3 year Warranty on their GPU cards.
If the GPU card is overheating then both Fans should be running and not one. Make sure there is nothing that might be interfering with the GPU fan like a cable or wire.
If the fan starts rotating after your give it a physical push to the Fan blades, then it is probably a defective fan.