Thanks it worked out when i tried below point1

quick OPC 2022.1
.net framework
Its Windows console app
We are attaching the license under quick opc provided when we purchased the OPC
we are running under admin priveleges

Dear OPC support,
we are encountering below error when fetching tags. Please guide on it.
An OPC-UA operation failure with error ID 'OpcLabs.UAEngine=1' occurred, originating from 'Opc.Ua.Core' and with depth of 2. The inner exception, of type "OpcLabs.EasyOpc.UA.Engine.UAEngineException", contains details about the problem. at OpcLabs.EasyOpc.UA.IEasyUAClientExtension.Read(IEasyUAClient client, UAReadArguments readArguments)
at OpcLabs.EasyOpc.UA.IEasyUAClientExtension.Read(IEasyUAClient client, UAEndpointDescriptor endpointDescriptor, UANodeDescriptor nodeDescriptor)
at QC_conel.Program.Read_Multiple(Boolean isUpdateDb) in \\sharemedia\Source Codes\APIs\Maximo Integration\PLCData\QC conel\Program.cs:line 79
UA SDK error (Opc.UA.ServiceResult=0x801A0000) in 'ApplicationInstance.CheckApplicationInstanceCertificate'. OPC UA service result - {BadCertificateUntrusted}. The certificate is not trusted.
+ The error occurred while creating or checking the (client) application instance certificate. Check event log entries for errors and warnings.
+ Suggestion: Check the trusted peers certificate store for the presence of the application instance certificate. This error can happen if the instance certificate is in the application instance store, but not in the trusted peers certificate store.
+ The certificate generator path was "E:\Scheduled Tasks\Maximo Integration\QCs_PLC - Copy\Opc.Ua.CertificateGenerator.exe".
+ This is an engine-level error. It is unrelated to any specific target server connection.
+ Connection attempt #1; last connected at 1/1/0001 12:00:00 AM (local); unconnected for 00:00:00.2190000.
+ The client method called (or event/callback invoked) was 'ReadMultiple[1]'. == Activity Trace ==
Following ( events were gathered during the action on activity ID [11], in the order of first occurrence:
SDK trace: Checking application instance certificate.
SDK trace: Checking application instance certificate. CN=QC conel, DC=SRV-Tabadul
2*Exception: {Opc.Ua.ServiceResultException} Self Signed Certificate is not trusted. IssuerName: CN=QC conel, DC=SRV-Tabadul
SDK trace: Certificate 'CN=QC conel, DC=SRV-Tabadul' rejected. Reason=BadCertificateUntrusted
SDK trace: Writing rejected certificate to directory: [Directory]%CommonApplicationData%\OPC Foundation\CertificateStores\RejectedCertificates
Exception: {System.UnauthorizedAccessException} Access to the path 'C:\ProgramData\OPC Foundation\CertificateStores\RejectedCertificates\private\QC conel [60641CF8AA864A0B665E3C6F8E9233EECC6730AC].pfx' is denied.
SDK trace: Could not write certificate to directory: [Directory]%CommonApplicationData%\OPC Foundation\CertificateStores\RejectedCertificates UnauthorizedAccessException 'Access to the path 'C:\ProgramData\OPC Foundation\CertificateStores\RejectedCertificates\private\QC conel [60641CF8AA864A0B665E3C6F8E9233EECC6730AC].pfx' is denied.'