Have reviewed your install. If you press F12 it opens the developer console. The validation will throw a browser error if the HTTP request fails. In this case it does due to the following query you're using being invalid.
Code:
SELECT COUNT (*) FROM `#__comprofiler` WHERE `cb_fbo_id` = '[value]'
The above should be as follows.
Code:
SELECT COUNT(*) FROM `#__comprofiler` WHERE `cb_fbo_id` = '[value]'
Notice the space after COUNT is now removed. SQL doesn't like a space after function name. I've went ahead and fixed that for you. Next the following error is then thrown by the HTTP call.
Code:
Class 'Flycart\AxisMeta\Admin\Helper\Plugin' not found
The above is a fatal PHP error being thrown by "AxisMeta Renderer" 3rd party Joomla system plugin. Once disabled in Extensions > Plugins the query ajax validation works fine. I suggest contacting the developer of "AxisMeta Renderer" regarding the above error or simply don't use it.
krileon
