This is simply not true.
The cache purge button is there, on the top admin bar, under the FVM menu.
If you have disabled the wp-admin bar, that would have been your choice…
Be sure to purge your cache, as well as cloudflare or any cdn service.
You may be seeing outdated versions of some scripts.
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FVM is a plugin for developers and advanced users, as shown in the main page.
It’s also explained on the HELP tab inside the plugin, that you need to configure the plugin manually for it to optimize your site and scripts.
Of course, if you do nothing, it does nothing as well.
It’s no longer something you install and hope that it works out of the box.
FVM 2 had a few automated settings that frequently caused issues due to the fact that it was automated, and now they are manual.
On FVM 3 all you need to do is to read the help section and configure the plugin.
The plugin is not dead. On the contrary, it keeps evolving. Thousands of users have already reconfigured the version 3 plugin and obtained much better speed results as compared with FVM 2.
Of course, if you do not have the minimal understanding of how optimization works, and how scripts can create conflicts while merging, and if you don’t want to bother with configuring things… then yes, this plugin may not be for you.
A “revenge” review, when you didn’t even ask for support properly or cared to solve the problem in any way, doesn’t really going to do any difference.
I am actively helping people reconfiguring the plugin and they are all happy about the results so far, provided they simply ask.
Either way, your choice.