This was an insane thing for me to have missed. 😢
In the new XOAI implementation (gdcc/xoai-5.0.0-RC1), validation was added for the "from=" parameter, rejecting the request if the date supplied is before what the OAI Repository thinks is the "earliest date stamp" in it. *) But the RepositoryConfiguration is still initialized with the default value of
.withEarliestDate(DateProvider.now())
and it's never reset in the Dataverse code. And "now" in this context means the time the OAI service was initialized.
Which in turn means that the server is going to reject any incremental request from a client that hasn't successfully harvested since the last time this Dataverse application was restarted (!).
Straightforward to fix; and we may want to consider applying the fix as a patch to our (Harvard) prod. before 5.13 is released.
*) Is this validation really necessary? I'm accepting full responsibility for missing this; and I'm all for fixing it - if nothing else, we want to advertise the correct date in the Identify verb. But I'm not sure I understand the point of rejecting requests on account of this; and I'm not seeing this spelled out in the OAI spec. May not be looking in the right place, etc.