Hey! Over the past few days there was a big site change that resulted in a bit of a lag (specially for cached items like HA's). has this resolved for you?
If not, remove all items from your HA, save it, refresh, and create your new avatar! make sure you're using only items that are in your inventory and have not selected 'ALL' onsite items!

How long are you letting the page load before trying to convert? I had that request pop up a few times but it would go away after I waited ~30 seconds (due to caching) and was able to get into wardrobe just fine. However, computer/internet connectivity differs & you may just need to let it fully load once! So you may want to fully clear your browser cache & try to re-open wardrobe, letting it sit on the page a while to see if it will actually load.
If that doesn't work, or your avatar continues to not load, Click HERE to reset your avatar to the default, and then click wear.
If both those options don't work, this may be more than just caching/single user issues! You may want to check out this forum: Problems & Bugs to see if anyone else is dealing with this issue. Or you can file a ticket if nothing else is working!
