If RFI (request for information) is approved, but change order is not approved. What can be the reason?

Reason could be cost, the cost for the change order might be too high and would entirely affect the project schedule.

Cost or time required to implement change will exceed project schedule.

Sometimes change order gives rise to entirely new sub-project with-in that project, which certainly not falls into the viability of the organization. Another reason could be that change order tends to alter the original contract, which requires much more time and cost.

RFI approval does not necessarily mean approval of change in scope and/or schedule impact. In case RFI has been issued and approved for clarification on technical matters without impacting project specs etc. then change order may not be entertainted by the client.

I have faced above situations in one of my projects. Please revert incase some for clarification is required.

RFI is only a request for information, there could be multiple reasons for a culminated change order to be rejected, cost, production schedule could be one of them. An approved and completed RFI will not automatically provide an approval for a change order.

RFI does not change value of PO or contract, it is just a request to the vendor for information. Even if it is approved, the change order may not necessarly be approved. The change order maybe rejected for reasons like cost, schedule, new technology, no expertise etc.