August 2020, during the mayhem of the coronavirus pandemic, WordPress released version 5.5 — and subsequently a fair amount of websites “broke” in some fashion. The sites 3Cstudio saw that had issues were still using a legacy theme called Startbox, which had held up to many years of updates (including the massive jump to version 5.0), even though it had been several years since it received updates and further development. Kudos to the developers for their sound coding and stable structure!
The short-term solution I found was to use a Plugin to revert back to a previous version of WordPress (in this case, version 5.4.2) — that plugin was: WP Downgrade | Specific Core Version. This worked great, getting WordPress back to useable state, but did not work (well) for multi-site WordPress installations… the wp-admin area lost all of its styling so the stark black-n-white interface was a jumble of unnumbered lists/menus and random content overlapping other content boxes.
The long-term solution is to replace all instances of Startbox. It was slated for replacement anyway, as after 2020 it was not going to work well with WordPress v.5.0 (2018) anyway. This 5.5 version release has sped up the process a bit, but should be beneficial in the long run, as sites will now be guaranteed to get their themes converted by 2020’s end. And here’s hoping that the end of 2020 is easier on many of us than the start of 2020! Of course, that is just after what looks to be a tumultuous November election. 😮 So we shall see!