String Trimmers

About 2 months ago, I bought a Husqvarna LD128 trimmer and an LE720 edger attachment. The trimmer has worked fine. I finally decided it was time to do edging. I easily removed the trimmer. However, I couldn't get the edger accessory to fully insert. The release button doesn't get far enough in to pass through the hole like it should. Furthermore, I can no longer re-insert the trimmer that was originally attached.

It seems to me that the shaft on the lower attachment is going as far in to the coupler in the upper shaft as it will go. I'm worried that the coupler in the upper shaft has somehow been misaligned or otherwise knocked out of place.

Any suggestions would be appreciated.