Changelanguage Stopped working

Sometime in the last two months, changelanguage simply stopped working for me. When I look at the html source, it is simply not there. Even the html DIVs are missing. This may have happened when I updated my extensions and didn't notice the problem at the time. I have uninstalled the extension and tried to go back to version 3.0.0 and 3.0.1 with no luck. I checked all the setup (module, page layout, site structure) and it is as it was when it was working.

Any ideas how I can debug this? I see nothing in the logs.

Changelanguage Version: 3.0.2 (also tried 3.0.1 and 3.0.0)
Contao Verison: 3.5.14
Haste Version: 4.14.2
MultiColumn Version: 3.3.6
NamespaceClassLoader Version: 1.0.2

Thanks for any help,

Allen

You'll only see something in the HTML source, if you integrated the language switcher module. Is that the case?

Also try to deactivate the internal cache while installing new extensions.

Thanks for the responses.

"You'll only see something in the HTML source, if you integrated the language switcher module. Is that the case?"

-> Yes. I created the module and added it to the page layouts.

"Also try to deactivate the internal cache while installing new extensions"

-> I tried that, but no change.

Note that this had been working for a very long time without problem.

Any other ideas?