To confirm the reason this slowness may occur check the following and then try and reopen UBS:
Make sure all PCs are following our system requirement
Ensure that on all PCs, the Defender Firewall and Antivirus software is off.
Make sure the system version is the same for all servers and the client pc.
If it still takes longer than expected to open the system, it could either be your internet connection is slow or there is an issue with your VPN connection and this is beyond our support. Please check with your IT department for further assistance.