Excel not opening after macOS Tahoe 26.0.1 update
Lost Excel from Microsoft 365 all the other apps are fine. Believe this is the rust of OS update to Tahoe 26.0.1
Can't open Excel
[Edited by Moderator]
MacBook Air 13″, macOS 26.0
“Microsoft Office up to date, works fine, except for old (2020) Excel file, which it says cannot validate developer. Problem since upgrading to OS Tahoe 26.1.”
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MS Office Seen as Unidentified Developer:
So, where did you purchase this? It if is NOT from a retailer nor from Microsoft, then it may be an invalid license key —officially meaning it is fraudulent and malware. Developers of software often create their own kind of files, making them be seen as scams. So, if purchased elsewhere, you should:
- back up your Mac using Time Machine Backup
- uninstall MS Office
- purchase MS Office from your local Retailer or directly from Microsoft
- Install that version
- create a backup again
System Integrity Protection:
Back in the day of High Sierra, this whole “unauthorized developer” became a big ordeal, and the only way around that was to use the following link, or use a command in Terminal. This may do the job: Open a Mac App from an Unknown Developer - Apple Support
Scan your Mac for Malware:
Use MalwareBytes for Mac --- This is software that searches for malware/adware. So, scan with it and then remove what is found. Once removed, uninstall MalwareBytes for Mac. Then restart the Mac.
Downloads:
Note:
Microsoft at times can be little picky and demand that your only option is to call them. That typically occurs when you need assistance with getting into your account. But, being not the case, they ought to run you right through it. I’d say it’s no more than a glitch. So, ask Microsoft for a new key while in the chat.
Go here: Contact Us - Microsoft Support
