I use emacs org-mode heavily, but don't usually use emacs otherwise. I am still using emacs 25.3 but also have 26.3 installed. This evening, after a Windows Update (likely cause of the problem?), when I restarted emacs (runemacs) under 25.3 I received the following error message.
error: Required feature ‘ht’ was not provided
I have also tried running it under emacs 26.3 and receive a slightly more helpful error message "c:etc. etc. /AppData/Roaming/.emacs.d/elpa/ht-20190924.704/ht.elc failed to provide feature ‘ht’"
I have not changed or updated any of the packages in several weeks. So, it is unlikely to be a change in org-mode or emacs.
I have experimented around with a variety of different approaches but without any luck. Among other things I restored the elpa files and my customization files from a back-up of a couple of days ago without getting a different results.
package-list-package with emacs 25.3 works with the error message, and I can upgrade the packages (2) that can be upgraded. However that also makes no difference to the error message I receive when I restart emacs. This does imply that ht.elc is working since, without it, you can't install packages since the new package needs to have its hash code checked. If I delete the ht package and try to update packages without it, updates fail on the hash code check.
package-list-package with emacs 26.3 is a whole other problem which might be why I'm not using it. TLS connections fail, and it can't connect to melpa, orgmode.org, etc.
In any case, I can't load my customization files and can't use org-mode at this point. Anyone have any ideas, questions or suggestions?
Thanks in advance.
This is a solution, without being an answer.
Using package-list-packages, and looking at the details for the ht package, it showed an "alternative" version being available from melpa; same release number. So, I chose to install it and a refreshed list of packages then showed that I had the same version installed twice.
I then closed emacs and restarted it. It started with a similar error message, but this time referring to the dash package. Repeated the duplicate install process as described above.
I again closed emacs and restarted it, and now it loads and runs correctly.
I had tried previously to just delete the ht package from the elpa directory, but doing that and attempting to install a fresh package resulted in a shower of errors. I don't remember all of them but at least one of them was that emacs was unable to read the package signature.
So, problem solved, but I still have no idea why it occurred in the first place, since it had been weeks since I had updated any packages, nor why the restore of the directories from several days ago didn't solve the problem.
And before anyone yells at me about moving to the current emacs, I have now installed the missing dependencies and am running on 26.3.