Hi there and welcome
Can you as the first step, power off the printer, then open it where you put the ink in and using a damp cloth clean out all the rollers and areas inside the printer to remove any ink that's there causing this.
Once done, allow it to dry for 20 minutes, close it back up, power it on and tell me how it now prints please.
There are two types, the thermal and the ink models.
You have the one where you put the thermal paper in it and no ink?
Ok, for this model you need to use the cleaning sheets.
If you do not have any, you can purchase them from here
It will tell you where to find a store close to you eg: Office Works.
Then once you have the sheets you
Press and hold the ON/OFF button to turn the machine off.
Hold the machine by the front, and firmly lift the DK Roll compartment cover to open it.
Remove the DK Roll.
Remove the backing paper and feed the edge of the cleaning sheet into the printing unit until it reaches the area shown by an arrow on the sheetInsert the sheet without removing the stickerpart part of sheet (you will see this on the actual sheet).
Check that the printing surface of the cleaning sheet is upward.
Close the DK Roll compartment cover and press the ON/OFF button (on/off button) to turn the machine on.Press the Feed button for more than one second. The roller spins by 4" (10 cm). The adhesive face of the cleaning sheet removes the stain on the roller.
If you do not press the Feed button for more than one second, the roller spins only 1/3" (8 mm).Dispose the cleaning sheet after use.
This will then remove the streak for you
I will mark this question to remain open in the event you do not have the sheets, so If you have continued problems, or would like any additional information or assistance, please do not hesitate to let me know.
And if you can take a second to rate my service by clicking one of the stars at the top of the screen then submit, that would be greatly appreciated.