Whenever Alexa says "Sorry I'm having trouble understanding right now, please try a little later," it means there's a connection issue between your Echo device and Amazon's servers.
There are many possibilities to the cause:
1. There may be a partial outage at Amazon.
2. Your internet provider may have a partial outage.
3. Another device is monopolizing your entire internet connection. Apple iPhones and iPads are notorious of taking over your entire bandwidth when it does its iCloud backups. It basically makes all other devices' connections extremely slow, like 28.8k dial up slow with extremely long ping times and 90% packet loss. I've seen this happen in person on a 300Mbps cable internet line. You might ask how can one iPhone take over all 300Mbps? I don't know, but Apple does it.
4. The many networks between your internet provider and Amazon may have an outage. This has happened many times before. When it is very wide spread, you may hear about it on the news.
When there's a complete outage, the Echo will show a red light and say something like "I'm having trouble connecting to the internet." It's a different message than what you heard. This generally means there's an issue with your WiFi router or your Echo just needs to be power cycled.
Regarding item #3 above, you might say your internet is fine because your streaming music is still playing or your Netflix movie/Youtube video is still going. Those types of things are buffered. That is it can continue to play for a minute or so even when your internet connection drops completely. You can test that yourself. Next time you're streaming from Pandora or Spotify, pull the plug on your WiFi router. Your music will continue playing for a minute or two. When it comes to Alexa, nothing is buffered. Alexa does not know what you are going to ask next so it can't get the answer before you ask. When you ask a question, Alexa needs to get the answer from Amazon's servers. If anything prevents that from happening right there and then, you'll get some sort of error message.
Here's an interesting read about internet problems from ARS Technica:
In summary, for 18 months no one can figure out why the entire village's internet goes out every morning at 7AM.
https://arstechnica.com/information-technology/2020/09/old-tv-set-interfered-with-villages-dsl-internet-each-day-for-18-months/