Okay, maybe it’s just a lost in translation thing from you to me, but it’s not my router. This was working fine when I was with my other ISP and showed activated and good for 90 days like Let’sEncrypt states.
Then due to circumstances outside my control, being that my former ISP sucked and would never fix their issues, I switched to using my AT&T mobile hotspot which was NAt’d causing me to be double NAT’d, and left my DDNS off due to this. I recently got onto a new ISP, (living in the country here in Texas, USA, we have very limited choices unless we want to use Satellite service - Never gonna happen) and I was having to go round and round with ASUS just for them to release my DDNS name from the old ISP’s IP address I had. Was just recently that ASUS, asuscomm.com, finally got their act together and released the IP from the DDNS name I registered with them. So, everything was working normally as far as the DDNS name to IP address was concerned, but the Let’sEncrypt went into this Updating mode.
I had been waiting to hear back from my new ISP as to what ports they may or may not be blocking on my Static IP address. Come to find out, they were indeed actually blocking port 80.
All this has transpired since I created my initial post here. I’ve been in IT System Administration for over 25+ years, so I know a bit about what I am doing, but since I don’t control my ISP or how they configure or setup their issued IP addresses, I had to wait for an answer.
And thanks for the “rip”, Rip, on needing to be motivated to secure my FTP port or move to FTPS. I have been doing some testing, and between my router and this new ASUSTOR device, I have temporarily enabled Port 21 for FTP access between the two. But thanks for the encouragement to not leave open an unsecured port to the outside world. 
So, with all this said and done, this post can be closed with the answer being the following for other folks having a similar issue in the future:
My new ISP was in fact blocking inbound traffic on Port 80. I got a notice from the owner of the ISP this morning that he updated my IP to allow inbound traffic on Port 80. So, once he enabled that, my router’s Let’sEncrypt changed from Updating to OK and I have my 90 certificate once again working.
So, I guess you could say my post was a bit overzealous and I should have had a bit more patience. But I’m in IT, so patience is always a bit lacking.
Thanks for the comments and for trying to look into my issue.
Lat