System error 21:10
Explanation 
Service Station failure
Recommended action 
The possible cause could be: 
1. The steps counted by the Service Station motor are not consistent with the expected length of the current movement. 
2. The Aerosol Fan has reached its maximum current limit. If your printer actually has an Aerosol Fan then the printer is Very old. This fan has been removed (dis-included) from the printer assembly long ago. Service may be required to replace the Service Station and/or related components. 
3. The Service Station motor has shutdown because of blockage. Service may be required to remove Debris, adjust or to replace the Service Station and/or related components. 
CAUTION: 
HP offers no technical support for persons who are not qualified to provide HP Warranty repairs. Example: Replacing the Trailing Cable on any Designjet Printer is not a user service. This is very technical and requires HP-Qualified Service Technicians in order to qualify for HP Warranty coverage. In any case, one who renders repairs to HP Designjet printers (self-help) is strongly recommended to refer to the applicable HP Service Manual, updates and service notes. However, please be aware that HP Service Manuals, technical updates and service notes are published available only for HP-Qualified Service Technicians.