When I went to bed last night my project could npm start the dev server with no issues.

When I woke up this morning, nothing I tried would make npm start run it.

(1) Branches from the day before would not load. It shows a blank page.

(2) Reinstalling node modules does not help. It loads a blank page.

I get a bunch of warnings in the console that all look irrelevant to me:

react_devtools_backend.js:2540 src\_helper\auctioneer.ts
  Line 1:10:  'postOptions' is defined but never used         @typescript-eslint/no-unused-vars
  Line 4:10:  'isAllEmpty' is defined but never used          @typescript-eslint/no-unused-vars
  Line 57:9:  'typeIndex' is assigned a value but never used  @typescript-eslint/no-unused-vars

src\pages\messages\Messages.js
  Line 26:12:  'showSettings' is assigned a value but never used  no-unused-vars

src\pages\post\Post.tsx
  Line 47:10:   'first' is defined but never used                   @typescript-eslint/no-unused-vars
  Line 76:14:   'convertToFormalStyling' is defined but never used  @typescript-eslint/no-unused-vars
  Line 142:14:  'inspecter' is defined but never used               @typescript-eslint/no-unused-vars

src\utility\prettyText.tsx
  Line 1:36:  'joinClasses' is defined but never used  @typescript-eslint/no-unused-vars

src\utility\process.ts
  Line 57:9:  Expected an error object to be thrown  no-throw-literal

src\utility\utility.ts
  Line 110:9:   'booleanValuesDescribingQuality' is assigned a value but never used                @typescript-eslint/no-unused-vars
  Line 113:9:   'startPoints' is assigned a value but never used                                   @typescript-eslint/no-unused-vars
  Line 113:44:  Array.prototype.map() expects a value to be returned at the end of arrow function  array-callback-return
  Line 118:9:   'endPoints' is assigned a value but never used                                     @typescript-eslint/no-unused-vars
  Line 118:42:  Array.prototype.map() expects a value to be returned at the end of arrow function  array-callback-return

According to me, I changed absolutely nothing between my dev server working 15 hours ago, and starting it this morning.

What should I try?

Occasionally (but not always) I see a message:

DevTools failed to load source map: Could not load content for chrome-extension://hnfanknocfeofbddgcijnmhnfnkdnaad/content.js.map: HTTP error: status code 404, net::ERR_UNKNOWN_URL_SCHEME
DevTools failed to load source map: Could not load content for chrome-extension://hnfanknocfeofbddgcijnmhnfnkdnaad/requestProvider.js.map: HTTP error: status code 404, net::ERR_UNKNOWN_URL_SCHEME

I'm totally lost. What could it be? There isn't even a lot to Google as I took no actions to cause this. If anyone has a diagnostic suggestion thats welcome.