BTW: Is the Euro value calculated for the time the Bitcoin transaction was performed (in the past) or always with the current exchange rate?
It's the previous value at the transaction's timestamp.
That column will only show if you ticked "
Download historical rates" in "
Tools->Preferences->Fiat" settings, by the way.
Why is "No data" shown?
Electrum failed to fetch the historical rates for those particular transactions.
Ref:
github.com/spesmilo/electrum/blob/master/electrum/exchange_rate.py#L802-L803How can I "repair" this?
Some price API sources that Electrum use cannot fetch rates on particular dates
But since it's a third-party API, the reason can be anything like problem with the data they sent to your client or related to your connection to those sources, etc.
Try "
Bitfinex" source for EUR, it works on old and new transactions at my end.