All Limesurvey Versions are somehow "web versions", it is a web application that needs to run on a web server. So "web version" doesn't say much. I assume that you are referring to the SaaS version hosted by the Limesurvey GmbH (vs selfhosting).
As far as I know, you can not install plugins and addons on the SaaS version yourself. You will need to get in touch with the support (go to the website and open a support ticket, most respondents here in the forum are users that help users, we have no insights into the internal process of the Limesurvey GmbH).
Help us to help you!
Provide your LS version and where it is installed (own server, uni/employer, SaaS hosting, etc.).
Always provide a LSS file (not LSQ or LSG).
Note: I answer at this forum in my spare time, I'm not a LimeSurvey GmbH employee.
