eBuy is where GSA Schedule buying actually happens day to day: an agency posts a request for quote restricted to holders of a specific SIN, and only those contractors can see it and respond. You cannot browse into it without a Schedule contract behind you; it is not a general opportunity search tool the way SAM.gov is. Once you hold a Schedule contract, watching eBuy for requests under your SINs is a routine part of using the vehicle, not an optional extra.

In a sentence

"This RFQ was posted to eBuy and is open only to contractors holding an active Schedule contract under the listed SIN." If you are not already a Schedule holder in that category, this particular opportunity is not reachable, no workaround.