It seems to happen in regular 'cycles' with 3rd-party resources for any large system - an ebb and flow of those who make those resources. Within the Joomla community it seems to happen every 3-4 years.
Over the past few months we've seen a LOT of smaller companies get bought out and others have merged their offerings with others. Along with this also comes those that just 'dissapear'. One day you are using their extension and the next they just aren't there. There might be some advance warning, like infrequent updates or lack of response on their support channels, or the web site might just go offline.
The bad news is that it's time once again to reconsider what extensions are being used on your Joomla site and possibly switch to new extensions (or custom solutions).
The good news is that this cycle not only forces you to clean-up your site of older non-supported extensions, it also usually ushers in a new round of development and extension options.
We alerted you at the end of 2017 of several extensions that we felt were not wise choices for the long-term future and we've recently had to add a few more.
If you haven't checked-up on the developers that make your extensions lately, this is a very good time to do so. And if you're not sure about any of them please contact us and we can share our personal experience with you.
IF we host your site we are watching your extensions and can usually avoid a 'surprise'. We have been able to see the changes within the companies and find alternatives before they just dissapear.
If you need assistance with your web site to get the your extensions up-to-date just reply by email and we'll take a look at your site for you.