I receive this error in both Sketchup Pro and Layout. On both my MacBook Pro and Mac mini.
What version of SketchUp are you running?
Sorry, Version 23.1.341
FYI, 3D Warehouse, Extension Warehouse and Geolocation all work fine.
I have got same result when I try to check, even with SU2021… but don’t worry too much, there is NO newer version than this: 
• SketchUp Help : Release Notes
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Why the release notes? I’m confused.
Please update your forum profile with that information along with the current OS vesion
Release Notes are always denoting the latest, recent version.
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I see the same problem, and I’m checking with colleagues about that.
Worse than that, after failing to check for an update SketchUp then crashed, though I am on Sonoma, which has a couple of crashing issues of its own.
Thanks Colin, your prompt replies are appreciated.
maybe too many people are checking for updates 
are you using Version 23.1.341 ?
if so it’s normal. there is no newer version.
I have version 23.1.340
I can understand that if it’s the latest, it won’t offer me a new version, but in this case it says something like “You are currently using the most recent version”, but here the message says “A problem has occurred while searching for updates. Check your Internet connection and try again.” with a “Cancel” button and a “Try again” button.
almquist7
I’m having the same issue on my MacBook Pro. Did you find a solution?
You can download the latest version from the website. https://help.sketchup.com/en/downloading-sketchup
Have the same problem with Version 21.0.392. Can download but that is not the same. I do not want to reinstall all extensions.
if you want to install 21.1 on mac then no, you won’t have to reinstall the extensions.
just download the installer, open it, and copy the thing into your application folder. it’ll replace the existing applications but your extensions and all the other bits are someplace completely different.
now, if you want to install 22, 23 or soon 24, you’ll have to either copy your extension folder (and hope) or reinstall them all.
updating a minor version won’t remove your extension. only major (=yearly) versions will, since they are technically a new install (I have 3 sketchup installed on my mac right now, side by side)
by the way, if you’re staying on 21, I’d advise you to keep the installer at hand somewhere. on a drive, in your archives…
soon, when 24 is released, they’ll likely remove 21’s installer from the website. if you need it later, you’ll be stuck.
I hope so.