I am stuck on the Amazon Sellers Site. Please help.

I am adding a product to my Amazon store. This is also my first time having an Amazon store. So, I guess it is only expected that I might run into issues. I have run into an issue.
I have a already set up the GTIN number and bar code for my new product. I have downloaded the barcode image from gs1 for later use. I do not need to use the bar code, I understand, until I set up the for FBA and I have not gotten to that point yet.
Anyway, I got this mysterious error on the seller central as I was trying to set things up:



After asking around, I was suggested this possible solution. I was told that it might be a glitch in the system caused by Amazon aggressively trying to make sure that products have brand names (which, by the way, is not really connected to the error) and that if I typed N/A for the brand name, this would clear up the Product ID issue.
https://www.youtube.com/watch?fbclid=IwAR1GqIzFJ01W8MexKXmESFpEoPzrHOwIYgvIlTrP5A8KMjtsu44KKlJy990&v=VnDepaYeEtA&feature=youtu.be
This video seems to address a very similar problem. But it is talking about an FBA error and I am not FBA just yet. I am only trying to make my first sale. Still, I gave it a shot. I typed "N/a" for the brand name and the error went away. But now I have a different problem. At the top of the page, I see this.



So, now I am stuck.
Any suggestions?

 

I am not stuck anymore.

The solution, it seems, is that a GTIN-12 is a UPC.