From Daedalus FAQ.
I am stuck at the loading screen, it says “Syncing blocks” at X.X%. What should I do?
Please note that blocks are synced in steps, each of which might take up to a minute. If Daedalus is stuck at X.XX% value for several minutes, please check your internet connection and try to restart Daedalus. If the internet connection is stable and syncing is still freezing after the restart, please follow the instruction below to reset the blocks in your PC.
Type %appdata% on the explorer’s address bar
Open Daedalus folder
Delete the content of DB-1.0
On the Finder’s menu bar select Go
Click Go to Finder…
Type ~/Library/Application Support/Daedalus
Delete the content of the DB-1.0 folder