I am using jmeter almost every day.
Today when I try open my test plan (.jmx file), I get error (screenshot below).
Yesterday it worked with no problem and I did not install anything new, new plugin or new version of JMeter.
I found similar issues here, so I tried to install jmeter-plugins-manager-1.1.jar then update other plugins but no changes, still same error.
I tried newest version of JMeter 4.0 but it didn't help neither.