pages will not open on early 2011 MacBook Pro

When you just launch Pages by itself without attempting to open any document, or you are attempting to open a document that you recently received from someone? Which case?

1. From the menu : About This Mac, what version of High Sierra are your running? Click on the displayed version number to also show its build version. You should see 10.13.6 (17G14033).
2. From your /Applications folder, single-click on the Pages application, and press option+command+i. What is the version number?
3. Single-click on the Pages document you are attempting to open, and press option+command+i. What is the creation date?

1. Current Pages documents show the early-2011 MacBook Pro as unsupported hardware, and that model is also on Apple's vintage and obsolete products list. That may be the reason that neither Pages, nor Pages for iCloud can open the document. High Sierra also requires Pages v7.3 through v8.1, and if you are attempting to use an older version, it probably won't let you.

Is your MacBook Pro still keeping current time per the menu bar when it is on battery? That is a very suspicious file creation date, though manually changing the creation date on an empty Pages v10.1 document here to December 31, 1969 at 00:01 did not prevent Pages from opening it — even with a bogus creation date.

Take that Pages document to another Mac with Pages v5.6 or later on it, and see if opens there. If it doesn't, you have a damaged Pages document, and there will be no resurrection of it.

Your 2011 MacBook Pro would still be the rage if Apple never produced another Mac afterward, or stopped releasing newer versions of macOS. Time f-bombs us all, and as Apple intends to remain in business, they are not deliberately causing your Mac to be 9 years old and hardware-wise, incapable of running current operating systems.

Good that you got this solved.

You are welcome.