Well a possible solution anyways! I've hit a few bugs with it since I started using it, but it's such a handy tool it's always worth fixing it than cross posting manually! So, some bugs + fixes I found, I hope they help anyone else getting frustrated by this neat little program!

Clicked icon; new page doesn't open to WZL
This tends to happen back when WZL was being DDoS, or seemed busy. Refresh the art page, let it load FULLY, try again. If not working, check if WZL is down. If it is, wait a few, obviously. If not, try a hard refresh on the art page (control + F5) to fetch new cookies. Note, sometimes the new page is a bit slow, so try clicking and waiting a few!

Clicked icon; broken page
Hard refresh the art page (control + F5) attempt again. If still failing, check WZL for being slow/unresponsive. Hard refresh for good measure. If still not working, uninstall from extensions, and re install.

Image transfer failed
Try again! May need to hard refresh (control + F5) the art page you are trying to cross post. Check your internet connection for being generally laggy. (I only had this once, and it was my connection being a derp and lagging)

Crossposter icon is gone!
I've seen this a few times, just had it happen. Go to your extensions, uninstall re-install. Open the thing you want to crosspost in a new tab (important!) it should be there.

Have heard that this does not always work. A combo of:
--Uninstall waxposter-reinstall
--uninstall & reinstall chrome
--restart computer
--reset internet connection
Have all been suggested. Always try the first fix first, it's the easiest and should work.

if you have found bugs & solutions let me know. I'd love for there to be a nice little database of bugs + fixes for other people using this! Also feel 100% free to repost/link/share this tiny list, add to it, and whatever you like. It's just to help people having problems!