Question Preview doesn't work

I tried that fix, but got the error 0 Class 'IpHelper' not found even after upgrade to 3.9.21.

Hello,

I think you have forgot to put at the begining of /kunena/forum/message/message.php the following line (at line 16) :

Yes forgot that, but I still have the identical error after correction. On Xampp I cant detect any PHP error either in error log.

I will try to install xampp on a virtual machine on windows 10 to try to see if i'am able to reproduce this issue

I have installed xampp with Php 7.4.9 but the preview works as usual

P.S. : in firefox open the console (by pressing F12), open tab nammed console, then check that the XHR is selected on the right and opne preview tab. Expand to see details on ajax query which is in red and open answer :



The image is too much much compressed, you have else an example here : media.prod.mdn.mozit.cloud/attachments/2...36586/console_01.png

Many thanks! In Firefox the error looks at this:
POST
www.mysite.com/kunena/topic/edit.raw
Status
500
Internal Server Error

VersionHTTP/1.1
Överfört45,58 kB (45,08 kB storlek)
Cache-Control
no-store, must-revalidate, post-check=0, pre-check=0, no-cache
Cache-Control
public
Connection
close
Content-Disposition
attachment; filename="topic.edit.json"
Content-Type
text/html; charset=UTF-8
Date
Thu, 27 Aug 2020 05:22:51 GMT
Expires
Mon, 1 Jan 2001 00:00:00 GMT
Last-Modified
Thu, 27 Aug 2020 05:22:51 GMT
P3P
CP="NOI ADM DEV PSAi COM NAV OUR OTRo STP IND DEM"
Pragma
no-cache
Server
Apache
Transfer-Encoding
chunked
X-Powered-By
PHP/7.4.6
Accept application/json, text/javascript, */*; q=0.01

Accept-Encoding
gzip, deflate
Accept-Language
sv-SE,sv;q=0.8,en-US;q=0.5,en;q=0.3
Connection
keep-alive
Content-Length
11
Content-Type
application/x-www-form-urlencoded; charset=UTF-8
Cookie
joomla_remember_me_9a39bb92733fe0206ef0db6fb0ac=h2F0YdTddfJe68bQ.omDqtTvFTZbr24ptBmti; jc_homepage=; 1f9f1d328e5f608f9cb163bfe1e0567b=99f5c6aa7abdf19bb4c50c493cd9f4c9; joomla_user_state=logged_in; PHPSESSID=9f935dc11daa4851a79ab1639386c65e
Host
www.mysite.com
Origin
www.mysite.com
Referer
www.mysite.com/kunena/allmn-diskussion/5...e/reply/1274437.html
User-Agent
Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:79.0) Gecko/20100101 Firefox/79.0
X-Requested-With
XMLHttpRequest

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