We use a few "generic" DKIM keys when validating the DKIM record. However some ESPs don't have those generic keys and give you a very specific key to verify with.
For this reason when you click into the mailbox with the DKIM warning you'll see a text input asking you to add the the DKIM selector.
If you hover over the "i" icon you'll see the following image and instructions.
Follow the steps you get your custom DKIM key from your DNS and click verify, you'll be off to the races!
From the image below, what you want to be doing is finding the "Selector" from your DKIM string and pop it into the text field.
If you're DKIM is validated and working on any third-party verifier https://dmarcian.com/dkim-inspector/
You should not need to worry, we remove the DKIM check each time any update is made to the mailbox to protect it from any sense of failure
Your only requirement here is to re-add it and verify it.
But if you don't want to, just confirm it works on the DKIM inspector or other tools.
Just to note, there is no effect of any deliverability if your DKIM records actually exist and reflect on 3rd party tools, but don't reflect on Smartlead.
DKIM/DMARC/SPF are protocols on a DNS level not an email sender level