I am having a similar issue with my DarkCoin wallet. I got it back in 2015, and I have never had a similar issue, actually.
I have some tips with regards to the Dashcore wallet, i will let others comment on the Dash Electrum issue ''cannot read file''.
First make sure that there is actually a balance on the Dash blockchain receiving address, please check your Dash receiving address(es) here :
https://chainz.cryptoid.info/dash/
If there is indeed a balance on your Dash address and the Dashcore wallet is not showing that, i would advice the following :
- make a backup of your wallet
- delete peers.dat file
- download latest Dashcore wallet version 0.17.0.3 from here :
https://www.dash.org/downloads/
- initiate a reindex on your blockchain, this can be done from within your Dashcore wallet (Tools - Wallet Repair - Rebuild Index) or through the commandline as a -reindex option behind dash-qt.exe in the target of your desktop shortcut.
If that does not help, you have two other options :
Option 1
- make a backup of your wallet
- download latest Dashcore wallet version 0.17.0.3 from here :
https://www.dash.org/downloads/
- delete everything except your wallet.dat file and let the Dashcore wallet download and sync the whole Dash blockchain from scratch
Option 2
- make a backup of your wallet
- delete peers.dat file
- download latest Dashcore wallet version 0.17.0.3 from here :
https://www.dash.org/downloads/
- download and install the Dash bootstrap from our Dash lead developer here :
https://github.com/UdjinM6/dash-bootstrap
and let the Dashcore wallet sync that Dash blockchain from start.