Not only on the wallet, but the same issue on my znode. Either reindex required or stuck in some block on both wallet and znode. I beleive there is some issue on the blockchain or in the code of version 0.13.5.7. The dev team of zcoin should do some troubleshooting. Everyone can try removing 'chainstate' folder and 'blocks' folder and re-download the blocks from the network, see what will happen, should be able to reproduce the same issue menetioned here. I have to stop the running of my znode currently.