Solution will not load

Strange event. Server is running great. No errors to mention. Most clients connect fine. So, from time to time people just cannot connect. Let em explain:
Click on servoy icon on desktop. connection is made, wheel churns, login box comes up. Log in, here is where it sticks.
The solution does not load.
In the bottom left courner, it says ‘ready’ , bottom right says ‘SSL’
I can see the person as connected in servoy-admin.
But the solution does not open.

What would prevent a solution from opening either on the local pc or internet connection? Would upload speed on the internet connections have any bearing? Local firewall? Anti-virus software?

Keep in mind this is intermittent. Most times all can connect fine.

Look forward to any help.