If your baby has the pink (!) at the bottom of the screen it means she is upset. Cuddle, tickle or pat her until she calms down and then there's no problem.
I've seen a lot of questions about this.
Also, the more difficult the development exercise would be in real life, the harder it is for your baby in the game. Standing up, walking a few steps, clapping, laughing, all of the hard things need development points. Just take her to the playmat, or on a walk and make sure she is happy all the time. If she starts getting whiney, do something first! Holding her belly is usually a good sign that she needs a bath/diaper change/ food. Try the one that is the first on your list of recent tasks for the baby, if that dumb bitch nurse tells you not to, do it anyway, she's usually wrong about that, but you will have to give the baby a bath/diaper changer/ and food to make her happy again.
Also, when you are doing a really difficult task DON'T TRY TO GET HER TO DO IT MORE THAN ONCE AT A TIME! Like when you're trying to get her to stand up with the toybox/playpen. She will just start screaming for a bath or something. If she does an exercise right, cuddle her, hand her a toy, talk to her, just basically let her know you are proud and that you love her a lot. (Just be her mommy, basically.)((PS. Crawling is not one of the hard tasks, but still reward her before you try to get her to do it again.))
I hope this all helped, it' practically everything you need to know, but I think I probably know a lot more, so just hit me up on here.