Hello,
a lot of thing could cause this problem. Since you are not the first to use this printer, it won't be easy to get the exact problem because you cannot explain what happened before the problem began.
Click the below link to view the manual for your Zebra 105SL.
Go to "troubleshooting" section of the manual and follow all directions therein. You will certainly get to the root of the problem by so doing. There are a lot of issue discussed on this section of the manual.
http://www.ausense.com/pdf/105SLusersguide.pdfThe user guide is in PDF format. So you need the latest version of adobe acrobat reader to be able to view the manual.
Also, you need to wait and allow the manual load completely, before you scroll through it for view. And you can print out the manual for future reference.
Please let me know of this doesn't help.
Regards.