"R cannot open because of a problem"

I've installed R 3.6.3 on a Mac OS X El Capitan, but when I try to open it I get a pop-up saying "R cannot open because of a problem". The message is not in English, but it's the same as this one (replace python2.7 by R): I've tried with older versions, I rebooted the computer, I uninstalled it and installed it again, but I keep getting the same message. FYI, I had anaconda installed before and I also tried uninstalling it.