Could you please post the console log for the first page, https://thai-notes.com/reading/lesson22.html That's where I believe the problem was. (That page passes data to the second page. It was the passing of data that had stopped working. The error on the second page which you've provided talks about "read properties of null". The data are null because they weren't passed from the first page. The log should look like this:
ResponsiveVoice r1.8.3
responsivevoice.js?key=vh25OFgw:340 isHidden: false
responsivevoice.js?key=vh25OFgw:341 Prerender: false
responsivevoice.js?key=vh25OFgw:402 Configuring
readloader-0.js:243 Version 1.3.0
responsivevoice.js?key=vh25OFgw:144 RV: Voice support read
The key text is "Version 1.3.0". If it's missing, it's definitely a caching problem - either with your browser (most probable) or with your ISP (pretty unlikely, but possible).
Incidentally, Incognito Mode does use caching, but the cache is cleared when you end the Incognito Mode session. May be worth closing your browser, reopening it and start another Incognito Mode session and trying again.
Fingers crossed.