There are 5 siblings on the property deed. We want to sell the property. One sibling is refusing to sign the listing agreement. Can we still sell the property?

You can go to court and seek a partition by sale. Where is the property located?

... Can we still sell the property?

Nope. As Ballengerb1 indicated, you will need a court order for sale, in a partition action.

Ownership of property, in common, is not a democracy. There is no provision for putting it to a vote.

Is the one sibling objecting to listing the property with an agent, or refusing to sell under any conditions?
What does that sibling think should be done with the property? For instance would he/she be agreeable to sale by owners or sale by auction?