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Hi Admin,
Good day to you!
Sorry for the late response, it was a holiday in our Billing Department region therefore it takes me more time than expected to contact them. Regarding your concern, the E5 (trial) Dev license is the legacy license and no longer support from our service. At the moment we are migrating our billing system from MOSA to MCA to utilize user experience with Billing session in Admin center. All subscription in the MOSA will be disabled and migrate to MCA. This might be the reason for your license disabled.
I totally understand this is not your expectation, and I tried my best to find any possibility to assist you; but this is all I can do since it was the confirmation from Billing Department for this legacy license.
Thank you for your understanding.
Best Regards,
Office 365 Support Engineer
Microsoft Customer Service & Support