Was able to create a user within CB > User Management on your install without any errors; only seeing notices and warnings. Not sure what to suggest. Are you still seeing this issue? If so please PM the exact steps you're taking to setup the account so I can reproduce your issue.
You do have the following installed plugins/extensions throwing deprecated notices or other notices during new user create.
EB Registration History
Code:
Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; getEBRegistrationHistoryTab has a deprecated constructor in /components/com_comprofiler/plugin/user/plug_ebregistrationhistory/cb.ebregistrationhistory.php on line 3
CB DiscreetDating
Code:
Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; getCBDiscreetdatingTab has a deprecated constructor in /components/com_comprofiler/plugin/user/plug_cbdiscreetdating/cbdiscreetdating.php on line 13
Geommunity Geocoder
Code:
Notice: Undefined variable: key in /components/com_comprofiler/plugin/user/plug_geommunitygeocoder/geommunitygeocoder.php on line 75
Notice: Trying to get property of non-object in /components/com_comprofiler/plugin/user/plug_geommunitygeocoder/geommunitygeocoder.php on line 85
Notice: Trying to get property of non-object in /components/com_comprofiler/plugin/user/plug_geommunitygeocoder/geommunitygeocoder.php on line 86
Notice: Trying to get property of non-object in /components/com_comprofiler/plugin/user/plug_geommunitygeocoder/geommunitygeocoder.php on line 101
Notice: Trying to get property of non-object in /components/com_comprofiler/plugin/user/plug_geommunitygeocoder/geommunitygeocoder.php on line 102
Acymailing Activity digest
Code:
Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; plgAcymailingActivitystreamemails has a deprecated constructor in /plugins/acymailing/activitystreamemails/activitystreamemails.php on line 3
Also "CB Activity To Kunena Transfer Automation" is marked incompatible and could be trying to load CB Activity incorrectly during user creation. Suggest contacting the developers of those plugins and having those issues addressed.