Error Adding Custom Clause

I’m preparing my first AST on OpenRent. I’m trying to add a large Custom Clause regarding gaining commitment from my tenants to uphold my Leaseholder’s Obligations to the Superior Landlord.

When I Cut and Paste it from Word into the Custom Clause box and press Add Custom Clause it comes back with “Error Adding Custom Clause”. I cannot find any any instructions for the Custom Clause box or any ecplanations of what the Error could be.

Does anyone know what causes Custom Clause Error?