Cannot see new created node?

Tough to suggest something in this case. This is a bit weird and never experienced it. Also, there isn't a point in creating a node - when you create a pool member, a node is auto-created. I would recommend skipping the part of creating a node.

try it again, what happens?

are you using multiple partitions?

tried with a different browser?

so many things it could be, try a bit more, i.e. via CLI and see what happens.

i usually start with node(s), create pool(s) then end with virtual server(s), the fact something is quicker doesn't always mean you should do it that way.

Yes , Even i have not seen such issue while working with F5 Version 11.4.1. It should create a node via GUI very easily. As in that case there is nor error screen too. Try with changing browser best option and try again . it will work surely.