Service Desk Plus 9409 frequently does not login with any user, Why?

Service Desk Plus 9409 frequently does not login with any user, Why?

We have installed ServiceDeK Plus 9409 with FOS, in this installation we have the following infrastrict with its role:
Virtual IP that senses the 2 SDP
Primary SDP: Windows Server 2016
Secondary SDP: Windows Server 2012 R2
File Attchments: Windows Server 2016

DATABASE.
CLUSTER MICROSOFT SQL 2014:
Virtual IP that feels the 2 Nodes
Node1 Primary SQL
Node2 SQL Secondary
Storage SCSI: Windows Server 2016

This FOS system worked the high availability test on the servers and automatically the second server goes into operation without affecting it but lately I present slowness in the operation of the Service Desk and falls of the operation even having the services up, we try to access the application and remains loading but not enter, another test we did to verify the connection of the database enter with the same user administrator and we put the wrong password and if detected it generates an authentication error that we verify the password, we enter the correct and it does not load the platform.
Basic troubleshooting tasks are performed, we restart service, verify logs, but we do not detect any problem that may be detected by the database or the application.
To correct this problem, the dedicated installation of the CLuster SQL database by means of nodes and independent storage was omitted. Where on another server the standalone SQL database was installed and it worked again importing the database through the .BAK

How can we know if this problem comes from the database?
We have already scaled it with the Manage Engine first level channel but we have not been able to detect which is the problem that causes the system to fall.

Thank you very much for your help.
Regards

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