DLS 1 W4 Assig 1 Ex 8. Unexpected Error

In the above indicated exercise" Linear Activation Backward", I encountered the following error (See attachment).
I cannot understand why there is a value missing in the cache, when in all previous exercises I got the result " all tests passed".

Can you give me a hint as to how to proceed?

Thanks very much


Sorry, already solved. A silly error. I used a wrong name for “cache”. Should be either activation_cache or linear_cache.