parsererror when I try to change my shipping prices

[kokod]

I am using Prestashop 1.6.1.24 with the default theme bootstrap.

I switched my Standard Delivery to Free Shipping but now when i try to change it back, I get a TECHNICAL ERROR:

Details:
Error thrown: [object Object]
Text status: parsererror

I have checked the JS console as suggested on an old forum thread but it doesn't seem to change regardless of what page of my site I am on and there doesn't seem to be a relevant error.

I've tried clearing the cache but it doesn't make any difference.

I am able to create a new delivery carrier and I can add as many shipping prices and weights as I want but I would have to add this new carrier to every product - over 700 so I can't do that.

Is there something I can do?

Thank you.

Attached are the error code and the js console

Edited May 16, 2022 by kokod
typo (see edit history)

[El Patron]

what is your php level? it's possible your hosting updated php level and your ps level is not compatible.  Because it's old version you may want to post in job section to get someone to help.  

[kokod]

7 hours ago, El Patron said:

what is your php level? it's possible your hosting updated php level and your ps level is not compatible.  Because it's old version you may want to post in job section to get someone to help.  

Thanks for the suggestion but it is still on php 7.1. The web host didn't update it.

I see people have been having similar issues in the past in other posts but no ever seems to get an answer as to why it happens or how to solve it.