They may be using something like Sift for security checking and something of yours was flagged. Source: almost 2 years ago

But sorry to break it to you, this has been done at a really large scale already although most consumers are not aware. One big player here is https://sift.com/ Almost every major retailer uses their service exactly for the reasons you mention. Source: almost 3 years ago

Reddit, for one. A pretty big list on their homepage. Source: almost 3 years ago

Apart from Admidio which has already been mentioned, another option to explore is CiviCRM. Source: about 1 year ago

As a software developer, I looked at some of what they did, and some of what is commercially available for candidates. The guy who won in the races I ran in was spending $1500/month for a website that was a simple brochure. Something that could be set up for even folks running for school board might be a simple hosted brochure/blog site with Wordpress as a front-end, with CivCRM keeping track of volunteers and... Source: over 1 year ago

Https://civicrm.org/ [this works with a cms like drupal, wordpress, joomla etc]. Source: about 2 years ago

So far I found Chatwoot, CiviCRM, Corteza, ERPNext, EspoCRM, Dolibarr, Odoo, OroCRM, Mautic, SuiteCRM and X2CRM and there are probably even much more available. It seems that Odoo and ERPNext are huge but also very flexible (with many extensions available). Source: over 2 years ago

If you are already using wordpress, you may also want to look at CiviCRM [https://civicrm.org/] for managing members etc. It is used by non-profit orgs. Source: over 2 years ago