I always get the "Invalid input" error whenever I try to use the NextToken param

Question

I'm encountering this annoying problem on Amazon's SP-API and its orders endpoint.

If I issue the sequent request:

https://sellingpartnerapi-eu.amazon.com/orders/v0/orders?MarketplaceIds=APJ6JRA9NG5V4&CreatedAfter=2021-03-01T00:00:00Z

I get the list of orders correctly, plus an additional, non-empty, field NextToken (which looks to be a base64 value):

{
    "payload": {
        "NextToken": "uLjySajlaBiaJqJYLDm0ZAmQazDrhw3CG1FJoDI1yzBUojdU4H46tsNI3HOI22PIxqXyQLkGMBs8VhF73Xgy+8ELbjnH8JQbw6wX5xiBJhyriSyQ7nsp20ySLLlBhTgvInTAy+XKVmRZBY+oaVuyc8QON+K1yc/Yt7kFSVBE95CdhRjq3crm1Mpe5xG0Blzcf2GLmUGyr9UGnxD0RJmrryegoU0IPZxXEM3PO3ipBZMfEJoEzZG6nXmssuEKQdDSMBO/reDY2s8epq+YYAk2AASk7RoO0Pg77YYXwRo+g8JiIXlRXylzxduZ3sLNMwtczEceQ+CtWMtAjbTFqrqX3UrzH1AqdxGeK++WzRQP+VFSZ/VYpjb2C0Ejd2syVxEcEw7io0mrdLAUwKwuhfytShM/3HXYSMjikIpa1fhf+aKDuvqjLOyRtg==",
        "CreatedBefore": "2021-04-28T09:10:09Z",
        "Orders": [
            {
                "AmazonOrderId": "...........",
                "PurchaseDate": "............",
                .....

According to the documentation, I just have to make a subsequent call similar to the previous, plus the aforementioned NextToken param (no alterations needed).

So this is what the next call should look like:

https://sellingpartnerapi-eu.amazon.com/orders/v0/orders?MarketplaceIds=APJ6JRA9NG5V4&CreatedAfter=2021-03-01T00:00:00Z&NextToken=uLjySajlaBiaJqJYLDm0ZAmQazDrhw3CG1FJoDI1yzBUojdU4H46tsNI3HOI22PIxqXyQLkGMBs8VhF73Xgy+8ELbjnH8JQbw6wX5xiBJhyriSyQ7nsp20ySLLlBhTgvInTAy+XKVmRZBY+oaVuyc8QON+K1yc/Yt7kFSVBE95CdhRjq3crm1Mpe5xG0Blzcf2GLmUGyr9UGnxD0RJmrryegoU0IPZxXEM3PO3ipBZMfEJoEzZG6nXmssuEKQdDSMBO/reDY2s8epq+YYAk2AASk7RoO0Pg77YYXwRo+g8JiIXlRXylzxduZ3sLNMwtczEceQ+CtWMtAjbTFqrqX3UrzH1AqdxGeK++WzRQP+VFSZ/VYpjb2C0Ejd2syVxEcEw7io0mrdLAUwKwuhfytShM/3HXYSMjikIpa1fhf+aKDuvqjLOyRtg==

But then I get this error:

{
"errors": [
    {
        "message": null,
        "code": "InvalidInput"
    }
]

}

Please note I'm using Postman to make the request.

I've already tried to remove all the unnecessary params, leaving only MarketplaceIds (required) and NextToken, to no avail.

What am I doing wrong here? Thanks in advance

Answer 1

I found the solution.

string encodedNextToken = HttpUtility.UrlEncode(nextToken);

Then, pass the encodedNextToken as nexttoken.