I want to send raw data to print, avoiding printer selection (fast print).
I am trying to use this helper provided by Microsoft: https://support.microsoft.com/en-us/
Fran_gg7, I had the same issue recently. Firstly, turn on the persistence of documents on the printer. This will allow you to see if the printer successfully received the print request.

You will see items in the printer queue and they will remain there.
In my scenario the print request was correctly being sent to the printer, however I was testing it on a laser printer that ultimately was unable to interpret the raw string data I was passing to it.
I tested the same output on a label printer that could understand the ZPL (zebra programming language) I was passing it and boom it worked fine.
Have a look at this for a detailed explanation
Hope this helps.