This is the debug msg that I think is related to the issue

WindowsPlayer(MSI) The specified license is not valid. at Zb.a (Nb a, System.String b) [0x0006a] in <5239c2b3ee7d4e3e4c326ca95b24eb03>:0
at Opc.UaFx.Client.Licenser.set_LicenseKey (System.String value) [0x00000] in <5239c2b3ee7d4e3e4c326ca95b24eb03>:0
at game4automation.OPCUAConnection.J () [0x0006e] in <7b9af2b18001b4bacaf73e0c6e424674>:0
at game4automation.OPCUAConnection.Connect () [0x0023e] in <7b9af2b18001b4bacaf73e0c6e424674>:0
UnityEngine.StackTraceUtility:ExtractStackTrace ()
UnityEngine.DebugLogHandler:LogFormat (UnityEngine.LogType,UnityEngine.Object,string,object[])
UnityEngine.Logger:Log (UnityEngine.LogType,object)
UnityEngine.Debug:Log (object)
game4automation.OPCUAConnection:Connect ()
game4automation.OPCUA_Interface:Connect () (at C:/Users/marti/Documentos/GitHub/UnityProjects/OPCUATest/Assets/game4automation/private/Interfaces/OPCUA4Unity/OPCUA_Interface.cs:465)
game4automation.OPCUA_Interface:OnEnable () (at C:/Users/marti/Documentos/GitHub/UnityProjects/OPCUATest/Assets/game4automation/private/Interfaces/OPCUA4Unity/OPCUA_Interface.cs:677)

(Filename: C:/Users/marti/Documentos/GitHub/UnityProjects/OPCUATest/Assets/game4automation/private/Interfaces/OPCUA4Unity/OPCUA_Interface.cs Line: 465)

Hello I am having the same problem and cannot see the beta version in the download page you are talking about. I'm using game4automation-Professional-2020.13.unitypackage and Unity 2020.3.1f