Error: Cannot find module 'prop-types'

I'm building a small CRA and want to use your react-metrics-graphics. So I've used yarn to add metrics-graphics and react-metrics-graphics. I have prop-types installed. I've built other CRA programs using prop-types so I can't figure out what to do here. Can you help?

Error: Cannot find module 'prop-types'
MetricsGraphics.js:159
at webpackMissingModule (c:\Users\Bruce\Dropbox\Projects\AcesTESTER\node_modules\react-metrics-graphics\build\MetricsGraphics.js:159:1)
at Object. (c:\Users\Bruce\Dropbox\Projects\AcesTESTER\node_modules\react-metrics-graphics\build\MetricsGraphics.js:159:1)
at b (c:\Users\Bruce\Dropbox\Projects\AcesTESTER\node_modules\react-metrics-graphics\build\MetricsGraphics.js:12:1)
at Object. (c:\Users\Bruce\Dropbox\Projects\AcesTESTER\node_modules\react-metrics-graphics\build\MetricsGraphics.js:75:1)
at b (c:\Users\Bruce\Dropbox\Projects\AcesTESTER\node_modules\react-metrics-graphics\build\MetricsGraphics.js:12:1)
at Object. (c:\Users\Bruce\Dropbox\Projects\AcesTESTER\node_modules\react-metrics-graphics\build\MetricsGraphics.js:35:1)
at b (c:\Users\Bruce\Dropbox\Projects\AcesTESTER\node_modules\react-metrics-graphics\build\MetricsGraphics.js:12:1)
at c:\Users\Bruce\Dropbox\Projects\AcesTESTER\node_modules\react-metrics-graphics\build\MetricsGraphics.js:31:1
at c:\Users\Bruce\Dropbox\Projects\AcesTESTER\node_modules\react-metrics-graphics\build\MetricsGraphics.js:32:1
at c:\Users\Bruce\Dropbox\Projects\AcesTESTER\node_modules\react-metrics-graphics\build\MetricsGraphics.js:2:1
at Object../node_modules/react-metrics-graphics/build/MetricsGraphics.js (c:\Users\Bruce\Dropbox\Projects\AcesTESTER\node_modules\react-metrics-graphics\build\MetricsGraphics.js:3:1)
at __webpack_require__ (http://localhost:3000/static/js/bundle.js:783:30)
at fn (http://localhost:3000/static/js/bundle.js:151:20)
at Module../src/components/Symbols/SymbolChart.js (http://localhost:3000/static/js/main.chunk.js:1356:80)
at __webpack_require__ (http://localhost:3000/static/js/bundle.js:783:30)
at fn (http://localhost:3000/static/js/bundle.js:151:20)
at Module../src/components/Symbols/SymbolCell.js (http://localhost:3000/static/js/main.chunk.js:1092:70)
at __webpack_require__ (http://localhost:3000/static/js/bundle.js:783:30)
at fn (http://localhost:3000/static/js/bundle.js:151:20)
at Module../src/components/Symbols/index.js (http://localhost:3000/static/js/main.chunk.js:1468:69)
at __webpack_require__ (http://localhost:3000/static/js/bundle.js:783:30)
at fn (http://localhost:3000/static/js/bundle.js:151:20)
at Module../src/components/App/index.js (http://localhost:3000/static/js/main.chunk.js:95:66)
at __webpack_require__ (http://localhost:3000/static/js/bundle.js:783:30)
at fn (http://localhost:3000/static/js/bundle.js:151:20)
at Module../src/index.js (http://localhost:3000/static/js/main.chunk.js:1605:73)
at __webpack_require__ (http://localhost:3000/static/js/bundle.js:783:30)
at fn (http://localhost:3000/static/js/bundle.js:151:20)
at Object.0 (http://localhost:3000/static/js/main.chunk.js:2525:18)
at __webpack_require__ (http://localhost:3000/static/js/bundle.js:783:30)
at checkDeferredModules (http://localhost:3000/static/js/bundle.js:46:23)
at Array.webpackJsonpCallback [as push] (http://localhost:3000/static/js/bundle.js:33:19)
at http://localhost:3000/static/js/main.chunk.js:1:57
./node_modules/react-metrics-graphics/build/MetricsGraphics.js
Module not found: Can't resolve 'prop-types' in 'C:\Users\Bruce\Dropbox\Projects\AcesTESTER\node_modules\react-metrics-graphics\build'

Start with node_modules/react-metrics-graphics/build/MetricsGraphics.js at line 159 and inspect the published package contents involved in resolving prop-types. Reproduce the import through src/components/Symbols/SymbolChart.js and verify that a clean CRA build no longer reports the missing module.

Written by the indexing model from the issue text.