So, here's my story. I made all my detail items ahead of time, i.e. flowers, plaques... and I was very excited how things were coming together. I iced my cake with a crusting buttercream the day before applying fondant. It was nice and smooth and looked great! Then everything went wrong!!!!
I tried panelling my fondant after watching Marina Sousa's craftsy class a few times over. I was unable to get the corners to smooth so you could see horrible seams. The fondant outside of that looked fab, at first. I let it rest for a bit, I was frustrated and needed a moment away after trying to figure out those darn seams. Within an hour the fondant started to wrinkle like it was sagging and I don't know why. So I have attached a picture for you to see my sad cake. Any thoughts or ideas of what I did wrong?? Anyone's advice would be greatly appreciated. I would like to try this again to get it right.

You had a crust on the buttercream. Maybe that prevented the fondant from sticking?

ditto. If the bc had crusted there was nothing for the fondant to stick to.

Triple ditto, the buttercream wasn't fresh and sticky. A great way to get it back to sticky is to mist it lightly. The other idea would be that your buttercream was not smooth in the first place but after seeing what a great decorator you are, I quickly dismissed idea number 2.

What brand of fondant did you use? Did you put anything on the crusted BC to help the fondant to stick?

The BC definitely needs to be very smooth, especially if you're panels are thin.

When I've done panel construction, I mix Wilton with whatever other brand I'm using. It's stiffer to start with. I also often add some Tylose to it. I roll the panels thicker than I normally do for fondant covering. I cut the panels and allow them to dry for at least 5 mins. before transferring them to the cake. I butt the panels so that the front & back panels are the full width of the side and the 2 side panels are just a bit shorter so that they are "inset". It forms a pretty clean join that way.

I've also used thinned melted chocolate to adhere the panels. I like the results.

This cake was done that way.



HTH
Rae

I misted the cake with Vodka before applying the fondant to make sure it would stick nicely. (Bronwen Weber Tip I Use) I am currently working with Satin Ice Fondant, I will have to try adding some wilton fondant to it. (I need to switch brands actually, I tend to melt Satin Ice with my HOT hands!)

Thank you for the Tips, I have been so disapointed in this cake! I am going to have to try to recreate it once I get these next few orders finished up and have a bit of free time.

Your help has been greatly appreciated. no matter how much I learn, I will never learn it all and this forum has been my savior along the way!

I have used the panel technique on my suitcase cake. I mixed the fondant (Duff's) with some modeling chocolate-it worked great because I din't have to color the fondant, as the chocolate did it for me. I rolled it out between 1/8" and 1/4" and cut each panel to size and then put it in the fridge for 5 min to slightly stiffen up. The panel kept it's shape beautifully. I also watched Marina's class. Did you pinch the seams together and then smooth them out? I found that the fondant w/ modeling chocolate was a lot sturdier and a lot more forgiving. So sorry this happened.

I always have the best luck putting fondant on a cold, hard cake. Which for me means an all butter ABC or SMBC, or a ganache. I haven't been able to use my usual ABC mixed with a bit of hi-ratio for under fondant-it just gets too soft for me. I know that others can do it, and more power to them, but i like a hard, smooth surface.

very cute design on it, though!

Thank you for your thoughts and advice. I will attempt this cake again, hopefully soon! I will not let this cake haunt my dream for long!!!!

I see this as just a technicality that you'll work through - because otherwise your cake is amazing!!