This article applies to you if you see "TH Sign" on the page where your signature should be.
The TH Graphics font included with most Checkjet deployments has default mappings for:
"S" (upper case S): "TypeHaus Signature"
"s" (lower case S): "TH Sign"
For most deployments using only a single signature image, the signature will be assigned to the upper case "S"/"TypeHaus Signature" image. Check your Project Information page to see what character your signature is assigned. If it indicates "S", then open your check template and use the upper case "S", which should show the "TypeHaus Signature" image on the screen.
Now print again to test if the signature appears where it should.