Rear indicator light bulb

Rear indicator and side indicator [same side] have stopped working. Went to replace the rear indicator bulb and stillnot working. Have taken the bulb and swapped with opposite side and bulb is working.
Not sure what else i can try.
Have lloked into fuse and doesnt seem to be one linked to the indicators.
Have also could reset the disconnecting battery and follow a procedure which i havent done yet as dont know if that would help.
Any help and suggestions welcomed. Thanks