Check your 802.11g radio profile and make sure that "High throughput enable (radio)" is active.
List all profiles: show rf dot11g-radio-profile
View profile: show rf dot11g-radio-profile DOT11G-RADIO-PROFILE-B
802.11g radio profile "DOT11G-RADIO-PROFILE-B"
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Parameter Value
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Radio enable Enabled
Mode ap-mode
High throughput enable (radio) Enabled
Channel N/A
Transmit EIRP 15 dBm
Non-Wi-Fi Interference Immunity 2
Enable CSA Disabled
CSA Count 4
Spectrum Monitoring Enabled
Spectrum Monitoring Profile default-g
Advertise 802.11d and 802.11h Capabilities Disabled
Spectrum Load Balancing Disabled
Spectrum Load Balancing Mode channel
Spectrum Load Balancing Update Interval (sec) 30 seconds
Spectrum Load Balancing Threshold (%) 20 percent
Spectrum Load Balancing Domain N/A
Beacon Period 100 msec
Beacon Regulate Disabled
Advertized regulatory max EIRP 0
ARM/WIDS Override OFF
Reduce Cell Size (Rx Sensitivity) 0 dB
Management Frame Throttle interval 1 sec
Management Frame Throttle Limit 20
Maximum Distance 0 meters
RX Sensitivity Threshold 0 dB
RX Sensitivity Tuning Based Channel Reuse disable
Protection for 802.11b Clients Enabled
Adaptive Radio Management (ARM) Profile ARM-G-PROFILE-B
High-throughput Radio Profile default-g
AM Scanning Profile default