For anyone who's reading here: if you are running into an

MD5 hashing algorithm is no longer valid

error when activating extensions/theme, make sure to update the "SuiteCommerce Extension Management" bundle to 2021.1.4.

{
  "type": "error.SuiteScriptError",
  "name": "15361",
  "message": "MD5 hashing algorithm is no longer valid",
  "stack": [
    "createError(N/error)"
  ],
  "cause": {
    "message": "MD5 hashing algorithm is no longer valid",
    "stack": [
      "createError(N/error)",
      "getMD5Hash(/SuiteBundles/Bundle 374045/ExtensionMechanism.Server/Services/FileApiSS2.js:338)",
      "reduce(/SuiteBundles/Bundle 374045/ExtensionMechanism.Server/CompilersMapReduce/JsCompilerMapReduce.js:336)"
    ],
    "name": "15361"
  },
  "id": "",
  "notifyOff": false,
  "userFacing": true
}

@Caleb Evans update extension management bundle it will help you out.