Issue with Outlook Signatures - ALERTS

Greetings. First-time poster here.

I am using Outlook for Mac v.16.41. I have created an Outlook signature and included my company logo, which is sourced from a .png file on my local HD. Every time I open a new email to send, the attached alert pops up. When I click "Yes," it pops up a second time. Clicking "Yes" a second time seems to rectify it as it goes away.

I am wondering if this might have something to do with the latest MS Office updates (which I stay on top of).

Is this caused by me using a local file image for my logo? Do I need to use a web-hosted image?

Thank you in advance for any help!

Jeff