I also had the same issue. It was not working for me before but i tried the retry button for 3 days and it installed by chance. I dont know , but i am lucky i think .  Please try it opening the dock tab and clicking the retry button till u get irritated or when u remember. If it gets the work done then no harm.

nothing happening while hammering ;)

This exact same issue started happening to me recently.  I’ve hit the Retry button a hundred times….nothing.  I think this is a Synapse 4 issue only. I hope Razer is aware and will implement a fix 

synapse3 works like a charm so they´ll need to look into it

Hi just download new version, I just end customer service ticket, the route was hard but they fixed for basilisk ultimate.