Can my Xero plan limit what BytePhase syncs?

Yes, in two ways. Xero’s Starter plan has a low daily API limit, so a bulk sync of many records in one go may use up that day’s quota. And tracking parts as Xero inventory needs a Xero plan that supports inventory; otherwise sync parts without stock tracking, which works on every Xero plan. Any record that fails to sync is listed with the reason in the sync view, where you can retry it.