Can’t open or save files after upgrading to Windows 10

Paul ... I am without hesitation, absolutely in support of your post.  I cannot understand the rationale of Microsoft's intent to force features on folks with no option to select and more importantly no way of remediation until Microsoft themselves puts out a "fix".

I run 2 businesses in Australia and NZ and like you have 000's of excel files.  I lost 2 weeks  trying to sort out my windows 10 crashing problems.  I had backups, restore points - you name it I had it - just so I could continue working.  I gave up the ghost when a windows update crashed my machine and I couldn't even log in.

In the end I paid a fortune to buy a new machine and sent my existing one (still under warranty) to be completed reinstalled back to Windows 7.  My new Surface Pro 4 has windows 10 and I purchased Office 2016.  Horror, horror I couldn't open anything.  Systematically working through (another 2 days lost) I trawled the internet and managed to get things working.  The biggest issue was not being able to open excel files.  My stress levels had been truly tested to the limit but I finally managed to resolve the excel problems and while there are still a few minor problems I can at least work.

Upgrade to Windows 11 - no way - I will let others prove it is working OK.

I understand your pain only too well!!

I have Thousands of Excel Spread Sheets and Hundreds of Calculators, lengthy Engineering & Building/Structural related Calculations, Workbooks and Drawings effectively negated as a result of the latest MS actions.

The 'Read-Only' function has been supposedly added to aid security ... for whom? Not for the general public, that's for sure.

I can accept the benefits of the 'Read-Only' function where documents are subject to review and in collaboration by numerous entities in Office/Workplace environments but not for the general public at large.

Whilst I believe it is MicroSofts' duty to provide us with functioning software incorporating a degree of security it should not be added carte-blanche without the means of readily circumventing the problems that have arisen.

There has to be a line between providing 'adequate' security as standard, and providing the option to improve security further ... should the Owner which to do so. Most Business Offices have IT specialists specifically employed to perform such tasks!

So ... this is becoming far lengthier than I anticipated, but suffice it to say having tried most, if not all methods purported to fix this problem ... None of them work .... none!

I have made Godzillion modifications along the way, no doubt creating more security holes than the 'Read-only' Fiasco was designed to prevent.

The good news is that modified Excel Documents can be saved, albeit as 97-2003 Work Books with potentially some loss in fidelity ... depends how adept you are in Excel. Bog standard spreadsheets save OK, those with a degree of previously unsupported formatting will still save but functionality will be reduced.

In closing,  MS time to put this problem to bed.

I feel your pain.  Everything will be fixed with Windows 11.  Thats how Microsoft does business.

I truly regret upgrading to windows 10. I cannot open a single file in Office (Word) and was unsuccessful with each of the suggested solutions.

When will this issue be resolved?

Microsoft won't help.  Apple won't help with ios and Google won't help with Android.  Everytime there is an update or upgrade to an operating system there are major problems with bugs.  It doesn't matter if its a computer or a smart phone.  The consumer than has to spend hours on the phone with someone with broken english who is trying to figure out a fix for the problem reading a trouble shooting manual.  It is all very frustrating.