I've removed my original post and apologize for having made it without checking the forum. The following is not really a justification for not having done so, but I submit it as an explanation.
Living here in Berlin and doing quite a bit of online shopping, I wind up tracing packages on the DHL website at least once a week. This has been the case for several years.
Today, for the very first time, the notification email I received from DHL took me to a page on which the search function didn't appear. This led me to do a bit of testing, which revealed a problem with the site, which was apparently brought to the attention of this list at the end of September.
As indicated, I've used that page literally hundreds of times without issue and have never encountered the problem before.
To be honest, when it happened today, since I've used the DHL tracking site so often, it never even dawned on me to see whether anyone else had encountered the problem.
My bad.