Adhesion is spoiled if the plastisizer floats on the surface. Wipe it away with alcohol before print.
There are many inks which adhere to rigid vinyl. Proper ink should be chosen taking the applications or desirable finish into consideration. As the heat resistance of the substrate is not good(50°C)(122°F), avoid heat drying.
Some vinyl stickers require long-term weathering resistance(several years by outdoor exposure).
Printers are advised to pay attention to choose the suitable ink.