I make my first 2-tiers fondant cake couple of days ago for my friend's granddaughter's birthday. 9" Strawberry and 6" vanilla cake. She called me this afternoon and said "I have to throw the whole cake away-it wasn't cooked." and I was like "Huh, are you joking?"

Apart from her 9" strawberry cake, I also baked 2-8" layers cake for my husband birthday. When I cut the top off, I did not see that cake was not cooked and of cos I did test the cake when it came out. When I put the cakes together, I put sugar syrup then ice it and then fondant.

I would have believed it if she said 1 tier wasn't baked but both? So I don't even know where I went wrong. I didn't get to see the inside of the cake because she threw it away. She said they started to cut the cake when the fondant decor was coming apart - it was raining and it was pretty humid but I don't think that will affect the cake.

Why did you put sugar syrup on it? Are your cakes usually dry?

I'm guessing she just thought the cake wasn't cooked from the simple syrup possibly creating a mushy cake. It's hard to know for sure without seeing it so I would scrap the simple syrup next time and just use icing and the fondant.

Humidity, sugar syrup and strawberry cake can get mushy. I just baked a strawberry cake for a friend this week and the thing was way too soft. I don't add syrup to my cakes so I imagine if I had I would have had the same results as you. Out of curiosity did you use a box cake and if so which one? I used a Betty Crocker mix and added a little Cream Bouquet extract. It would be interesting if you used a BC mix too.

Did you use real strawberries? Too much moisture and sugar will make a cake soggy inside.

no i make scratch cakes and never had any problems with it. and i also did put sugar syrup (water +sugar) onto my husband's cake. and i used strawberry puree.

if it was too soggy, wouldn't the cake fall apart? i never use any support for the cake at all and there were 2 tiers

Too many unanswered variables to give a good answer.
What was the cake recipe? What exactly kind of products did you use? Did you bake all the cakes all at once int he same oven? What kind of BC and fondant did you use? How long did it sit at your house before you gave it to them. How long at their house? Was the cake sitting outside?

And no support for the second tier at all? Wow, you got lucky.