I had the same problem in updating the Testimonials Widget on two separate sites. Each time, the plugin deactivated itself after updating. On one site, I had to recreate the Testimonials slider as the original one had disappeared completely. On the second site, the slider was initially invisible but then reappeared once I reactivated the plugin. Unfortunately, it had the default settings so I had to redo my customizations. Again, not a big deal, just a nuisance.
One thing I noticed, however, is that there is no longer an option in the settings to Disable Animation or control the Fade Out / Fade In speed. This is somewhat irritating since I had control over that in previous versions. Is this option now only available in the premium version?
That said, this really is an awesome plugin and the best Testimonials widget plugin I’ve found. It’s sturdy, easy to use, and does a nice job. I really appreciate the developer offering a lite version in addition to the Premium one, and I understand how much work has gone into maintaining this for the long haul. I am grateful :-)