back up not going thru

Hello,
My BackWPup job is not going thru.

I’ve tried the tip such as described on https://wordpress.org/support/topic/job-first-backup-has-started-but-not-responded-for-10-seconds/

where it is mentionned:
modify wp-config.php ( you can find this file in your root directory ), and before the line:
/* That’s all, stop editing! Happy blogging. */
add this line:
define(‘ALTERNATE_WP_CRON’ , true );

When adding this piece of code, I observe that the job is stopping during the process, whether I select BACKUP TO FTP or BACKUP TO FOLDER option.

Any further help would be much appreciated !
thanks
RP

DEBUG INFOS:
WordPress version: 5.6.2
BackWPup version: 3.8.0
PHP version: 7.3.12 (64bit)
MySQL version: 5.7.26-29-log
cURL version: 7.45.0
cURL SSL version: OpenSSL/1.0.1e
WP-Cron url: https://biokineticshealthsystem.com/wp-cron.php
Server self connect: Not expected HTTP response:
Status-Code: 429
Server: openresty
Date: Wed, 10 Mar 2021 19:54:58 GMT
Content-length: 0
Accept-ranges: bytes
Age: 0
Vary: User-Agent
X-cache: uncached
X-cache-hit: MISS
X-backend: all_requests
Strict-transport-security: max-age=31536000; includeSubDomains

Document root: /var/www
Temp folder: /var/www/wp-content/uploads/backwpup-797846-temp/
Log folder: /var/www/wp-content/uploads/backwpup-797846-logs/
Server: Apache
Operating System: Linux
PHP SAPI: cgi-fcgi
Current PHP user: root
Maximum execution time: 300 seconds
BackWPup maximum script execution time: 30 seconds
Alternative WP Cron: On
Disabled WP Cron: Off
CHMOD Dir: 453
Server Time: 19:54
Blog Time: 11:54
Blog Timezone: America/Los_Angeles
Blog Time offset: -8 hours
Blog language: en-US
MySQL Client encoding: utf8
PHP Memory limit: 256M
WP memory limit: 40M
WP maximum memory limit: 256M
Memory in use: 4.00 MB
Loaded PHP Extensions:: Core, PDO, Phar, Reflection, SPL, SimpleXML, Zend OPcache, apc, apcu, bcmath, bz2, calendar, cgi-fcgi, ctype, curl, date, dba, dom, exif, fileinfo, filter, ftp, gd, gettext, hash, iconv, igbinary, imagick, json, libxml, mbstring, mcrypt, memcache, mysql, mysqli, mysqlnd, openssl, pcntl, pcre, pdo_mysql, pdo_sqlite, posix, pspell, readline, session, shmop, soap, sockets, sqlite3, standard, sysvmsg, sysvsem, sysvshm, tokenizer, wddx, xml, xmlreader, xmlrpc, xmlwriter, xsl, yaml, zip, zlib`

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