When syncing a wallet that has been offline before a hard fork (consensus protocol upgrade) such as the one from version 1.1 to 1.2 so long as you have the new wallet running while syncing from earlier blocks to the post-enforcement blocks you will have no problem. It will sync all the way without trouble even though while syncing the earlier blocks you may still see some old version peer connections until the consensus upgrade block.
If you already synced past that block with the old wallet, such as during the network upgrade from 1.1 to 1.2 enforced at block 122513 on Sunday May 16th, 2021 it is easily fixed.
Anyone (or everyone) who took the wrong fork in the road because they didn't have the new wallet at the time can pretty easily get on track again (with the v1.2.x wallet installed) by (in the Debug Console or on the Command Line using veil-cli)invalidateblock 2b51811cfce06e8f6653bd2a954f0165e2df9b16c1c087e50b960f1fcfadac27 and reconsiderblock a8da4eace32cd5ce863a4a801e68c67c927ea96dad691c87d41c46c89b646e37
because at height 1221513 the bad block is 2b51811cfce06e8f6653bd2a954f0165e2df9b16c1c087e50b960f1fcfadac27 and the good block is a8da4eace32cd5ce863a4a801e68c67c927ea96dad691c87d41c46c89b646e37.
The good block at the previous block height 1221512 will be common between old and new wallets, and is c9f22bcbc522768ce5afda76aa804c718467cfa8262430f9ddd91d01faa699cb.
If you have an error message (in the Windows Qt wallet) mentioning forced_return.hpp you may like to try using the CLI (command line interface) wallet to complete your sync, and if necessary spend the balance to a fresh wallet version 1.2.2 or later (when available). This error is still being investigated.
It is possible that you may have lost connections to all peers on the network once you are correctly synced to the enforcement block height due to getting "peer banned" by other wallets because you had been sending bad blocks from your old wallet.
A peer ban can be bypassed via a VPN or Tor.
See: Getting peer connections on a new IP address via VPN or Tor browser proxy