Kindly obtain printer's model number, brand name, etc from behind & front of the printer,
then post it as a reply to your own message.
Sometime pressing the Print button for 10 seconds, will a print-out a paper that has all printer related info, you may try that as well.
Do not post s/n, password, public ip-address, or your email address, or other info that can identify a person, or do not post such info that is considered private/personal, etc.
it appears you may have selected/installed an incorrect printer driver for your printer, ( as you said its printing group of meaningless symbols ).
If other simple file are also not printing, which you know you printed earlier, then its incorrect printer driver.
if only one file is not-printing , then that file has incorrect data
or file-format is different, & file type need to be set.
Also try to post info on, what printing protocol you use to print, or printer is set to use what protocol ?