Sorry I am about 3 years late here. For the option to appear on your dashboard, you have to have the correct Meraki AP model. Some models are not compatible with the "PSK without RADIUS" configuration, so having them on your network will remove that option. I confirmed this with Meraki Support - also, 2 of my networks only have the MR55 and MR56 models, so I have that option on those networks but not the one where I have the MR34 models.
KB:https://documentation.meraki.com/MR/Encryption_and_Authentication/IPSK_Authentication_without_RADIUS
+ KB has a requirement that all APs in the network should be All APs in your network must be Wi-Fi 5 Wave 2 (MR20, MR30H, MR33, MR42, MR42E, MR52, MR53, MR53E, MR70, MR74. MR84), Wi-Fi 6 (MR28, MR36, MR36H, MR44, MR46, MR46E, MR56, MR76, MR78, MR86, MR45/55), Wi-Fi 6E (MR57, CW9162I, CW9164I, CW9166I) or newer.