It is a known issue and Zwift was “looking into it”. @Eric-Schlange-ZI claimed that it was working, but from what I (and it looks like you) can see, it clearly isn’t. Another user suggested that if those data are truly gone, then Zwift are probably running afoul of the GDPR. Doesn’t help us here in the US, but might be of use for some folks in the EU.
See here: Sharing : Only 250 of your latest ride records are kept on Zwift backend - #9 by Anders_Swanson