Thanks for taking the time to flag this, and I’m glad rolling back got your site working again in the meantime.
Please note that you can always check the fatal-error email WordPress sends the site admin when a critical error happens, or your PHP error log (your host can help you find it) to find the exact file/plugin path that triggered the error, which can tell you where the problem lives.
If the issue is only with LearnDash and you can confirm this through the log error as well, you can bring the issue to LearnDash’s attention to get accurate guidance as they might need to tweak a couple of things on their end to make their plugin compatible with WooPayment’s latest version.
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