ASP form throws javascript errors on search results page

On the search result page the plugin throws an error and just shows the spinning wheel:

TypeError: undefined is not an object (evaluating ‘d.style[a]=b’) asp-prereq.js:18:393

When I hit enter after change the input value (or click the magnifying glass) the console shows this error:

SyntaxError: The string did not match the expected pattern. asp-prereq.js:9:490

(Link https://firstfriday.biz.feelslikefriday.com/?s=learn&asp_active=1&p_asid=1&p_asp_data=1&customset%5B%5D=training-academy&customset%5B%5D=team-members&customset%5B%5D=product&customset%5B%5D=page&customset%5B%5D=post&asp_gen%5B%5D=excerpt&asp_gen%5B%5D=content&asp_gen%5B%5D=title&filters_initial=1&filters_changed=0&qtranslate_lang=0&woo_currency=GBP&current_page_id=1796 – note that you will need to click the search icon in the top menu to make the search form appear)

I’ve tried:

– Disabling all plugins bar ASP, the error remains

– Changed to blankslate plugin, added the ASP form to the search page and checked: issue still there.

– Emptying the search page template (bar header and footer), the error remains.

– Removed a lot of functions in functions.php that would potentially interfere with search the page but to no avail.

– Changed to Javascript source to non-minified and script loading method to classic in the Compatibility settings

It throws different error (but effectively caused by the same issue it seems):
TypeError: selector.indexOf is not a function. (In ‘selector.indexOf(‘asp_es_’)’, ‘selector.indexOf’ is undefined)

I checked error_log but that file’s empty

I inherited this website from a developer who magically disappeared and am still trying to understand how it’s all set up. It’s using blankslate theme with custom templates. I’m really hoping you ran into this issue before and it’s an easy fix!

https://firstfriday.biz.feelslikefriday.com/wp-admin/

U: tmp-admin
P: $Brlou*S6)B!fMh#^7l^*C34