A purchase made while signed out may not yet be linked to the Chatbot account you use on the other device.
Open Chatbot on the phone where you purchased.
Confirm PRO is available; restore the store purchase if necessary.
Sign in to Chatbot on that phone.
Open Chatbot on the web and use the same account and sign-in method.
Check access again. If it is still missing, send support your User ID and purchase receipt, and explain which device shows PRO.