If you have never tried before, have you chosen the correct media in printer preferences> paper quality> media settings area? If the card stock is not listed, choose a similar type, such as an index card or brochure, etc., so the printer "expects" thick paper.
You can also update drivers for your printer [https://support-printerdrivers.com/hp-officejet-pro-8600-driver-software/|HP Officejet Pro 8600] here
https://support-printerdrivers.com/hp-officejet-pro-8600-driver-software/