The Speedometer on my truck won't move from 0 truck moves fine how can i fix it? on 2005 GMC Sierra 1500

i use it to work and travel with out a problem but the speedometer arrow won't move from 0, i use my cellphone speedometer app to know how fast i am going, what can be wrong?

Asked by for the 2005 GMC Sierra 1500
poss inst cluster is bad,very common on GM products. the cost to repair is approx 450.00
Tks.. guess I take my truck to the shop...