Is it by the right side of the front panel?
Are you getting any sound of of your main speakers?
If so it may be the icon showing the 990 is in the headphone mode.
Page 37 of the manual.
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Epson 3500 3D projector
93" Carl's Place Flexiwhite DIY screen
Outlaw 976 Pre/Pro
Outlaw 7500 for LCR & L/R surrounds
1- Emotiva Mini X-A100 for rear surrounds
2- Outlaw LFM-1 EX subs
Oppo BDP-105 Blu-ray/DVD/SACD player
Outlaw LCR (Snell Labs) for center channel duty
Tekton Enzo XL L/R
4- Emotiva ERD-1s surround speakers
Monster HTS3600MKII power center