This is not a GenP-related issue. The answer can easily be found simply by referring to Adobe’s own support pages for Harmonize.

Harmonize is an AI-powered feature in Photoshop and relies on Adobe’s generative AI systems. As such, it requires generative credits to function, meaning it will not work if AI features are disabled or unavailable on an account.

Just a quick note as well, in case it isn’t widely known: Harmonize has always consumed generative credits.

When it was first introduced, it used 1 standard generative credit per generation. Now that Harmonize is in general release, Adobe clearly states in their documentation that it is classed as a standard feature and consumes 5 generative credits per generation. This is explicitly noted on Adobe’s support page here.

It’s worth noting that Adobe’s own documentation is inconsistent, as their marketing page still states that Harmonize uses 1 standard generative credit per generation. However, the Photoshop Help documentation and in-app behaviour show that Harmonize consumes 5 credits, which should be treated as the authoritative figure.

Because non-genuine methods result in accounts being classified under Free Membership usage, users only receive a limited number of generative credits per month. If people experiment with the feature, those credits can be used up very quickly in a single session.

This has also already been discussed on GenP Stoat and can be found easily by doing a simple search there for Harmonize.