check your package.json if it contains all needed dependencies and run npm install in the home directory of the project
if a package is missing you can add it with
npm install <package_name> --save
if you are using yarn run:
yarn add expo

check your `package.json` if it contains all needed dependencies and run `npm install` in the home directory of the project
if a package is missing you can add it with
npm install <package_name> --save
if you are using **yarn** run:
yarn add expo