Hello there. I Have the exact same issue. But if I have a look on the errorLog of my Server it says, that there are serious issues on several lines in the code of wp crm.

Can someone help me with this? Here is the errorLog I get:

[Tue Dec 11 13:31:21 2018] [error] [client 62.167.26.139] PHP Fatal error: Uncaught InvalidArgumentException: Unexpected data found., referer: https://mz-dienstleistungs.carvertising.ch/wp-admin/admin.php?page=erp-tools&tab=import
[Tue Dec 11 13:31:21 2018] [error] [client 62.167.26.139] Unexpected data found., referer: https://mz-dienstleistungs.carvertising.ch/wp-admin/admin.php?page=erp-tools&tab=import
[Tue Dec 11 13:31:21 2018] [error] [client 62.167.26.139] Data missing in /home/www/web323/html/Demopages/MZ-Dienstleistungs-AG/wp-content/plugins/erp/vendor/nesbot/carbon/src/Carbon/Carbon.php:909, referer: https://mz-dienstleistungs.carvertising.ch/wp-admin/admin.php?page=erp-tools&tab=import
[Tue Dec 11 13:31:21 2018] [error] [client 62.167.26.139] Stack trace:, referer: https://mz-dienstleistungs.carvertising.ch/wp-admin/admin.php?page=erp-tools&tab=import
[Tue Dec 11 13:31:21 2018] [error] [client 62.167.26.139] #0 /home/www/web323/html/Demopages/MZ-Dienstleistungs-AG/wp-content/plugins/erp/vendor/illuminate/database/Eloquent/Concerns/HasAttributes.php(709): Carbon\\Carbon::createFromFormat(‘Y-m-d H:i:s’, ‘01.08.1992’), referer: https://mz-dienstleistungs.carvertising.ch/wp-admin/admin.php?page=erp-tools&tab=import
[Tue Dec 11 13:31:21 2018] [error] [client 62.167.26.139] #1 /home/www/web323/html/Demopages/MZ-Dienstleistungs-AG/wp-content/plugins/erp/vendor/illuminate/database/Eloquent/Concerns/HasAttributes.php(732): Illuminate\\Database\\Eloquent\\Model->asDateTime(‘01.08.1992’), referer: https://mz-dienstleistungs.carvertising.ch/wp-admin/admin.php?page=erp-tools&tab=import
[Tue Dec 11 13:31:21 2018] [error] [client 62.167.26.139] #2 /home/www/web323/html/Demopages/MZ-Dienstleistungs-AG/wp-content/plugins/erp/vendor/illuminate/database/Eloquent/Concerns/HasAttributes.php(526): Illuminate\\Database\\Eloquent\\Model->fromDateTime(‘01.08.1992’), referer: https://mz-dienstleistungs.carvertising.ch/wp-admin/admin.php?page=erp-tools&tab=import
[Tue Dec 11 13:31:21 2018] [error] [client 62.167.26.139] #3 /home/www/web323/html/Demopages/MZ-Dienstleistungs-AG/wp-content/plugins/erp/vendor/illuminate/database/Eloquent/Model.php(234): Illuminate\\Database\\Eloque in /home/www/web323/html/Demopages/MZ-Dienstleistungs-AG/wp-content/plugins/erp/vendor/nesbot/carbon/src/Carbon/Carbon.php on line 909, referer: https://mz-dienstleistungs.carvertising.ch/wp-admin/admin.php?page=erp-tools&tab=import