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The html page hosting the EDS has to include a named <div> and that name should be passed to the EDS code.
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<div
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id="idpSelect">
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This error indicates that name supplied in the idp_config.js file does not exist.
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Some of the Discovery Protocol was supplied to the EDS, but this did not include a return address.
fatal.badReturnString 1.2.1
Text: Return parameter is not whitelisted
The return address supplied was not permitted based on the configured set of allowable locations.