More details required. Which wallet you are using? Is the wallet up to date? Synchronized?
i just closed electrum and launched it again and then the coins appeared. i didnt know i have to restart electrum wallet after every transaction. but this is good to know! thank you! You were probably disconnected from the network, hence why nothing was updated. As far as i know there's absolutely no need to reboot electrum every time you get a transaction.
The node you were using might went down, and you forgot to reconnect to another one?

Was this green dot by any chance red?