Custom Amazon Ads Won't Appear

I’m having a real problem with placing custom Amazon affiliate ads into my website’s posts. I don’t get what the issue is and I can’t seem to resolve it. It’s really driving me mad!

I want to use the use custom ads as you can pick and choose a specific layout of products you want to promote, and they come in a banner form.

I’ve just been trying with the standard custom first. To do so:

1) I log into my Amazon affiliates page
2) Log into Amazon.com
3) Find a product
4) Select custom
5) Copy the HTML
6) Go to Word Press
7) Add a custom HTML block to my post
8) Paste the HTLM there

And that should be it done but it won’t show up. When I click ‘preview’ nothing shows up. When I lick ‘convert to blocks’ just to have a see what happens, a little ‘play’ icon appears.

https://chrissoundlab.com/why-does-my-audio-interface-crackle/

Here is the post I’ve been trying it on, the custom ad should appear under the sentence ‘If doing the above didn’t resolve this, it may be time to upgrade your computer. Buying a decent solid-state drive is a good place to start.’

It doesn’t matter what post I try with though; the custom ads never show up.

Heres’ the HTML I’m trying to insert:

<script type="text/javascript">
amzn_assoc_tracking_id = "chrissoundlab-20";
amzn_assoc_ad_mode = "manual";
amzn_assoc_ad_type = "smart";
amzn_assoc_marketplace = "amazon";
amzn_assoc_region = "US";
amzn_assoc_design = "enhanced_links";
amzn_assoc_asins = "B08QBMD6P4";
amzn_assoc_placement = "adunit";
amzn_assoc_linkid = "ef88f7a4acb59fe44b37511554747532";
</script>
<script src="//z-na.amazon-adsystem.com/widgets/onejs?MarketPlace=US"></script>

If anyone could help me to resolve this, I’d be really grateful.

Thanks in advance!