First try in the Tools menu –> Rescan for transactions.
The blockchain will be scanned again, this may take some time. You will see a progress bar.
If that doesn’t help go to the menu Help/Debug Screen and open the Console tab.
At the bottom of this tab you will find an input bar. Type resetdatadirfull there and give a Return/enter.
The wallet will close. You will have to open it again manually after that. Then the wallet will download the blockchain again, this process can take 1 to 2 hours.
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