We stopped working due to non-payment and the contractor hired another sub.
If you have performed work on a real property in Pennsylvania pursuant to an agreement with the GC or property owner within the last five months, you have invoiced for the value of that performed work, but you have not yet received payment, you should be able to lien the property. I say five months because it sounds as if you worked as a subcontractor and would therefore need to provide the property owner with written notice of your work/intent to lien at least one month prior to filing the actual lien claim (which must be filed within six months of the date that you last performed contract work on the property).