Comodo Dragon informed me about v17.3 being ready. I chose to download and install this. Notification at top of the v17.2 browser showed a button, “Relaunch and Install”, so I clicked this. The browser closed, my normal desktop was present,… … … and nothing else happened. No installation. No installer displayed. The same comodo dragon browser v17.2 unchanged.
Several minutes later, I opened Comodo Dragon (still v 17.2), saw the same notification at top announcing that new version is available, so I chose it again. The same thing. Nothing happened after I clicked on Relaunch and Install.
(In any case, my version 17.2 still works excellently.)