To re-sync your windows wallet courtesy of - craigh

  1. Close wallet
  2. Backup C:\Users\<username>\AppData\Roaming\MonetaryUnitCore
  3. Delete C:\Users\<username>\AppData\Roaming\MonetaryUnitCore\Chainstate
  4. Delete C:\Users\<username>\AppData\Roaming\MonetaryUnitCore\peers.dat
  5. Delete C:\Users\<username>\AppData\Roaming\MonetaryUnitCore\blocks
  6. Restart wallet

2,3,4,5 replace <username> with your own username
that's assuming you're on windows with standard install
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to re-start & resync your VPS MasterNode do the following : you need to login to the vps
then do this

./mue-cli stop

cd .muecore

rm -Rf backups chainstate fee_estimates.dat mncache.dat netfulfilled.dat banlist.dat db.log governance.dat mnpayments.dat peers.dat debug.log blocks
cd ..

./mued --daemon

it will then start syncing