Change the SIG value
SIG parameter value determines the signaling protocol whether H.323 or SIP, and is used to determine the proper upgrade file that is downloaded. If you set the SIG parameter manually using the local administrative Craft SIG procedure, that value takes precedence over a SIG setting in a configuration file. A change in the SIG value might require a reset to the phone so that a new or different upgrade file can be downloaded to the phone.
As phone is having SIP so have to make these changes to phone and 46xx settings file. Also, make sure H.323 FW file must be inside server.
Please check the following documents for more details:
Installing and Maintaining Avaya Desk phone SIP for 9601/9608/ 9608G/9611G/9621G/9641G IP Desk phones:
https://downloads.avaya.com/css/P8/documents/100180585
Installing and Maintaining Avaya 9608/9608G/9611G/9621G/9641G/9641GS IP Desk phones H.323:
https://downloads.avaya.com/css/P8/documents/101009345