TABS- WYSIWYG editor does not appear

Hello, I have been a satisfied user of Tabs plugin for some time. However now I cannot use the plugin, because when I try to add content to a new tab the WYSIWYG editor does not appear anywhere, so I cannot enter anything.

It only appears on the default tab, but not when trying to add more tabs. I have also seen that in the new tabs the "active" tag is not also shown.

We do not know what could be happening.

Thanks a lot in advanced.