The sollution to your problem is simple: uninstall Messenger Plus! and follow the instructions presented by the sponsor program. If you don't see any instruction, it will probably means that your anti-adware programs damaged the unisntallation files. In that case, reinstall Messenger Plus! withthe sponsor and try uninstalling again, it will work.
After the ads have been removed, feel free to gie Messenger Plus! another try, just select "I refuse to install the sponsor" during installation this time

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