Purchasing AWS Reserved Elastic Cache node throwing ReservedCacheNodesOfferingNotFound error

I am trying to purchase a reserved node for Elastic Cache on AWS but on clicking Purchase Now it is throwing error ReservedCacheNodesOfferingNotFound.

Please have a look at below screens

While exploring this error on google I found a link to Amazon Elastic Cache API Reference in which details of this error is given as shown below:

ReservedCacheNodesOfferingNotFound

 The requested cache node offering does not exist.

 HTTP Status Code: 404

This information is also not enough to explain the problem clearly. I have not yet tried to purchase Reserved Elastic Cache node through its API but I am pretty sure that it will also throw the same error.

Does anyone have an idea that what does this error actually means? Is the instance type I have chosen is not available or I am doing something wrong here?

I am finally able to purchase the reserved elastic cache instance. In case anyone else stuck with same issue I thought of sharing the solution.

In my case I was not doing anything wrong it was a bug from AWS side. I reported this issue to AWS support team and they took more than 2 weeks to get it fixed.

So in case someone else face it just report it to AWS support team. I can't find any workaround to get it working.