If its connecting via mesh and it shouldn’t your options i would recommend would be -
Re-terminate the cable
Pin test the cable
Disable mesh on that AP or all AP’s if your not using it. (recommended as can cause network loops unless you only using the Alta switches which i believe may have STP could be wrong)
Ref STP - Coming soon - https://forum.alta.inc/t/stp-rstp-support/746?u=lincswifisolutions