By default, SSIDs on Cisco Meraki access points that are configured as WPA2 will utilize a combination of both TKIP and AES encryption. In most cases this will allow support for a wider variety of clients but some devices can respond poorly to these extra options.
Wireless beacons and probe responses will advertise AES or TKIP as encryption methods for unicast traffic and TKIP as the encryption method for multicast/broadcast traffic. This can be seen in the tagged parameters portion of the 802.11 wireless lan management frame of beacon and probe packets. The tags which provide this information are the "RSN Information" tag and the vendor specific "WPA Information Element" tag.
The WPA encryption setting is SSID specific, and can be found on the Wireless > Configure > Access control page as seen below:
This drop down will allow for "WPA2 only" or "WPA1 and WPA2". The "WPA1 and WPA2" option is the default selection and sets the SSID to perform in mixed mode. The "WPA2 only" option forces AES encryption.
If the device does not support AES, it is also possible to force TKIP only. Please contact Cisco Meraki support to configure this option.