Hi Peter284978702c1a,
Thank you for reaching out.
We checked your account and saw you use the Acrobat Sign Enterprise plan.
The default limit set is for 25 signers per transaction. For more information, refer to the following help document: https://helpx.adobe.com/sign/using/transaction-limits.html.
However, I would suggest you may check with the Acrobat Sign Enterprise support team if it can be customized or not.
You can contact the support team using the steps mentioned here: https://helpx.adobe.com/sign/using/adobesign-support-resources.html.
Thanks,
Meenakshi