Declined promotional Cashback

[#1]

TopCashBack have been chasing a promotional cashback of £63 that I never received.
This has been ongoing for about 4-5 months.
They have updated me today saying PlusNet have declined the cashback:

TopCashBack
"The reason given to us for the decline is "Another Marketing Channel"

I have used cash back apps before.  I purchased the product the same way I have done in the past and have never had an issue (not just plusnet, via various businesses). 

They stated this meant that I may have used another voucher (I didn't) or "cookies".

TopCashBack have confirmed that I have a registered click with them and I went through with the purchase (I am 6 months into a contract).

Please can someone look into this for me?

[#2]

Was there a Plusnet provided Reward card included in the offer?  That's a common reason for third party cashback rejection

[#3]

Hi 

Yes,  have attached the promotion

To be honest I only just managed to find this and have realised I received the Plusnet Card.
It is the £63 promotion that I have no record of.
Do you know if that come from PlusNet or TopCashBack?

[#4]

Anyone know anything about the above?

[#5]

Ah well.
Guess in the future I need to avoid PlusNet and TopCashBack.
Lesson learnt.