As a safety precaution always go to your PIVX data directory and backup your wallet.dat, Preferably on an offline location such as a secure flashdrive. Avoid online storage.
Now open your PIVX wallet, Select the TOOLS tab, select Wallet Repair in the drop down menu and lastly Select RESCAN BLOCKCHAIN FILES as seen in the image below
Your wallet should begin the rescan on the blockchain files for your missing transactions and your funds should show as normal. In some cases you may need to delete the old blockchain and completely resync everything. So if this tutorial doesn't work then please follow the blockchain deleting steps as mentioned in this one https://pivx.freshdesk.com/solution/articles/30000004661-wallet-crashes-or-has-crashed-and-now-won-t-launch-fails-every-time-what-do-i-do-