I am trying to download a new version of the Macbook, currently at 10.13. it will not let me and I have 10gb of storage, it will not tell me why?

OS Update will only show updates that are compatible with your model. You may have the latest operating system that your MacBook will support. This page lists the models that support OS 10.14 (Mojave):

macOS Mojave - Technical Specifications

The easiest way to identify your Mac is to open the Apple Menu and click on About This Mac. To find the model identifier (which looks like <MacBook10,1>) click on System Report, and it should open to Hardware Overview, where you can find it. Here is a page on MacBook models (and there are links to pages for Pro and Air models):

Identify your MacBook model - Apple Support

lin2320 Said:

"I am trying to download a new version of the Macbook, currently at 10.13. it will not let me and I have 10gb of storage, it will not tell me why?"

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Updating the macOS:

Determining which Update(s) will Install:

I. Verify Compatibility:

A. Start Here: Learn About Compatibility and how to Identify your Specific Mac Model - Apple Support

B. How to Verify:

I Reveal your Model:

What is the Model of your Mac? To find out...

1. Go to: Apple menu
2. Click: About this Mac
3. View: Second Line-Down

then...

II. Compare the Results:

See if the Model you found is shown here: macOS Mojave 10.14 - Hardware Requirements - Apple Support

III. If Compatible:

Back Up your Mac First:  Be certain you Create a Time Machine Backup of your Mac, so that way you can have something to restore your Mac from, should anything go wrong with the reconfiguration.