Datamax ST-3210 Operator's Manual page 25

Note: If automatic loading doesn't occur, try the following:
1) Ensure that the Printhead Latch is locked.
2) Press the PAUSE button (the On-Line Indicator will go 'Off') and
then repeatedly press the F2 button while gently pushing the
stock forward until the printer grabs the ticket.
3) Press the PAUSE button (to return to the on-line mode).
If the ticket was not fed to a proper position, the Media Sensor may need
adjustment; see Section 4 for details.
S-Class 17