As the fork on version v20 happened, all iOS mobile apps have issues with syncing.
The thing with the wallet is that the version you use is not connected to the network after the fork which happened last Thursday 14.12.23.
We have pushed the new version sometime before the fork was going to happen but unfortunately, the Apple Store has not yet approved our latest version which works post-fork.
Usually it does not take so much time and we still are awaiting the approval.
There is a solution for that as you can get the Testflight version of Dash we provided to the Apple Store.
The app is here: use that instead for now.
Once you download it and still cannot sync just go to the settings and rescan the blockchain.
Please contact the support desk if you still have issues with syncing.