Common reasons why you will not be able to add a new Company:
Only Arene subscribers who have purchased a Companies subscription may add new Companies in Arene.
Each Company purchased on a Companies subscription entitles a subscriber to add one more Company, where the company can be linked to a Data Source, and Collaborators can be invited.
Arene will explain the reason for you not being able to add a company through a warning message.
If you have reached the limit of Companies paid for in your subscription, you will need to purchase additional company plan units. Refer to: How to change my Arene plan
Delete an existing company will also free up a company unit, however this will mean that all accounting data will be deleted, and all Collaborators on the Company will lose access to the Company. Refer to: How to delete a Company from my Arene profile