Can someone with veds have a negative or inconclusive biopsy result?

Vascular Ehlers-Dan. If by veds you mean vascular ehlers-danlos syndrome, it is unlikely that a biopsy would be negative. Genetic testing exists to confirm a suspected diagnosis if the first biopsies were all negative and the index of suspicion is still very high.
98% DNA. Mutations sequencings are positive but there are other methods to detect the other 2%.