notepad++ xml validation returns shows "Missing schema or invalid namespace"

Question

I am trying to generate a xml batch for the automatic collection of invoiced amounts. I send you a shortened, anonymized copy of such a xml batch:

<?xml version="1.0" encoding="UTF-8"?>
<Document xmlns="urn:iso:std:iso:20022:tech:xsd:pain.008.001.02" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <CstmrDrctDbtInitn>
        <GrpHdr>
            <MsgId>20130122-000073</MsgId>
            <CreDtTm>2013-01-22T15:31:37</CreDtTm>
            <NbOfTxs>1</NbOfTxs>
            <CtrlSum>468.02</CtrlSum>
            <InitgPty>
                <Nm>Zondag N.V.</Nm>
                <Id>
                    <OrgId>
                        <Othr>
                            <Id>BE12ZZZ0123123123</Id>
                            <Issr>KBO-BCE</Issr>
                        </Othr>
                    </OrgId>
                </Id>
            </InitgPty>
        </GrpHdr>
        <PmtInf>
            <PmtInfId>20130122-000073-C000001</PmtInfId>
            <PmtMtd>DD</PmtMtd>
            <NbOfTxs>1</NbOfTxs>
            <CtrlSum>468.62</CtrlSum>
            <PmtTpInf>
                <SvcLvl>
                    <Cd>SEPA</Cd>
                </SvcLvl>
                <LclInstrm>
                    <Cd>CORE</Cd>
                </LclInstrm>
                <SeqTp>RCUR</SeqTp>
            </PmtTpInf>
            <ReqdColltnDt>2020-09-19</ReqdColltnDt>
            <Cdtr>
                <Nm>Zondag N.V.</Nm>
                <PstlAdr>
                    <Ctry>BE</Ctry>
                    <AdrLine>Wolkenweide 3</AdrLine>
                    <AdrLine>9999 SAPKREEK</AdrLine>
                </PstlAdr>
            </Cdtr>
            <CdtrAcct>
                <Id>
                    <IBAN>BE75132413241324</IBAN>
                </Id>
            </CdtrAcct>
            <CdtrAgt>
                <FinInstnId>
                    <BIC>BANKBEBB</BIC>
                </FinInstnId>
            </CdtrAgt>
            <ChrgBr>SLEV</ChrgBr>
            <CdtrSchmeId>
                <Id>
                    <PrvtId>
                        <Othr>
                            <Id>BE12ZZZ0123123123</Id>
                            <SchmeNm>
                                <Prtry>SEPA</Prtry>
                            </SchmeNm>
                        </Othr>
                    </PrvtId>
                </Id>
            </CdtrSchmeId>
            <DrctDbtTxInf>
                <PmtId>
                    <EndToEndId>20130122-000073-C000001-000001</EndToEndId>
                </PmtId>
                <InstdAmt Ccy="EUR">468.62</InstdAmt>
                <DrctDbtTx>
                    <MndtRltdInf>
                        <MndtId>2017.0001</MndtId>
                        <DtOfSgntr>2017-07-12</DtOfSgntr>
                    </MndtRltdInf>
                </DrctDbtTx>
                <DbtrAgt>
                    <FinInstnId>
                        <BIC>KREDBEBB</BIC>
                    </FinInstnId>
                </DbtrAgt>
                <Dbtr>
                    <Nm>Pietersen, P.</Nm>
                    <PstlAdr>
                        <Ctry>BE</Ctry>
                        <AdrLine>Eikenlaan 422</AdrLine>
                        <AdrLine>9999 SAPKREEK</AdrLine>
                    </PstlAdr>
                </Dbtr>
                <DbtrAcct>
                    <Id>
                        <IBAN>BE71456956298169</IBAN>
                    </Id>
                </DbtrAcct>
                <RmtInf>
                    <Ustrd>Energieafrekening t/m tweede k</Ustrd>
                </RmtInf>
            </DrctDbtTxInf>
        </PmtInf>
    </CstmrDrctDbtInitn>
</Document>

This xml batch should conform to the schema "pain.008.001.02". Being pretty large, I can only point to the Internet site where it can be found: https://www.isabel.eu/knowledge_base_ibs6/nl/03_client_solutions/04_ebanking/02_transactions/01_creating_transactions/isabel-6-supported-banking-file-formats.html under "SEPA Direct Debit (XML ISO20022) Pain 008.001.02".

I use the xml validator in Notepad++. I am requested to point to the schema file location on my local computer. Every time, I get the error message "Missing schema or invalid namespace", no matter what I try.

This seems a typical starter's problem, which it is. Could anyone help me to get started?

Han Schouten