Hi momumen,

create a report

<report 
    string="Request for Quotation" 
    id="report_purchase_quotation" 
    model="purchase.order" 
    report_type="qweb-pdf"
    name="purchase.report_purchasequotation" 
    file="purchase.report_purchasequotation"
/>

when we creating a template

<template id="report_purchasequotation">
    <t t-call="report.html_container">
        <t t-foreach="docs" t-as="o">
            <t t-call="purchase.report_purchasequotation_document" t-lang="o.partner_id.lang"/>
        </t>
    </t>
</template>

template id = report_purchasequotation its mention in the report's name and file.

"report_purchasequotation_document" - In this name, we create the exact qweb report template. then I think it will solve your issue. please check these with your custom modules.

Thank you