String Trimmers

I just got the Husqvarna 223L string trimmer. It's my first gas powered strong trimmer.

Was moving along pretty well, and, of course, the tiny amount of strong they had provided with the trimmer ran out. I had planned for that and purchased a spool of Husqvarna Titanium Force replacement string. This is one of the items the Husqvarna website listed as being compatible.

As the instructions were virtually indecipherable, I turned to the internet for help. Watched a video of how to replace the cable, and read a couple of how-to articles.

I would expect that I know what I'm doing at this point, but after spooling the string and putting it back on the trimmer, it keeps being thrown off. Everything seems fine, but after starting the trimmer, I throttle it up to speed and it throws the line off after a couple of seconds.

Obviously, I'm doing something wrong, but I can't figure out what it might be. Any tips?