It was due to some extra params being passed in the request after removing those it worked fine.
curl -X GET -G \ --url 'https://api.mindbodyonline.com/public/v6/client/clients' \ -H 'Accept: application/json' \ -H 'siteId: -99' \ -H 'authorization: auth token' \ -H 'API-Key: apikey' \ -d 'request.includeInactive=false' \ -d 'request.isProspect=false' \
-d 'request.lastModifiedDate=2024-11-01T00%3A00%3A00Z' \ -d 'request.limit=1000'