Issues with cookie retrieval in MusicKit JS

I built a player demo yesterday which I logged into and it worked great:

https://s.codepen.io/leemartin/debug/bKEeZL

Flash forward to today and the console is showing the following error:

Uncaught SyntaxError: Invalid regular expression: /(?:^|;\s*)Ag/zlbh4X32PLS+19Sv+ZlRv1OV8zxQZIMvaZ280bApwe9ljw+Xg+7TTwGiV3ZzcvWYogiEdYX+fSiRLWUiEi++IeqXZtkP9hUmg8B2AXlrWBOaoUfgu9wjGXJru7gFVpeoU6T2ZyALhaRcesnDVkznluIjiGTPta3ws3IQMYrBNzcAMiz5YngE4hn+P4Tci+domaZcK71jmC6l3yrGo2eiQvDy+aA6m/9/y6mdZRIWJsflK1A==.s=([^;]*)/: Nothing to repeat
    at new RegExp (<anonymous>)
    at Object.t.getCookie (musickit.js:13)
    at StoreKit._migrateStorageItem (musickit.js:13)
    at StoreKit._getStorageItem (musickit.js:13)
    at StoreKit.get [as storefrontCountryCode] (musickit.js:13)
    at new StoreKit (musickit.js:13)
    at new MusicKitInstance (musickit.js:13)
    at configure (musickit.js:13)
    at HTMLDocument.<anonymous> (musickit.js:13)
t.getCookie @ musickit.js:13
StoreKit._migrateStorageItem @ musickit.js:13
StoreKit._getStorageItem @ musickit.js:13
get @ musickit.js:13
StoreKit @ musickit.js:13
MusicKitInstance @ musickit.js:13
configure @ musickit.js:13
(anonymous) @ musickit.js:13

It looks like MusicKit is having trouble pulling a previously created cookie.

The website works fine when using a fresh incognito browser session.