Can't Add any new categories?

Fresh Install 1.5.6c
PHP 7.1

All of a sudden Can't add any new categories.

[14-Feb-2020 21:02:14 UTC] Request URI: /admin/categories.php?action=insert_category&cPath=, IP address: 100.2.167.42#1 trigger_error() called at [/home/teer/public_html/includes/classes/db/mysql/query_factory.php:171]
#2 queryFactory->show_error() called at [/home/teer/public_html/includes/classes/db/mysql/query_factory.php:143]
#3 queryFactory->set_error() called at [/home/teer/public_html/includes/classes/db/mysql/query_factory.php:270]
#4 queryFactory->Execute() called at [/home/teer/public_html/admin/includes/functions/database.php:51]
#5 zen_db_perform() called at [/home/teer/public_html/admin/categories.php:103]
--> PHP Fatal error: 1364:Field 'categories_promotion_id' doesn't have a default value :: insert into categories (sort_order, parent_id, date_added) values ('0', '0', now()) ==> (as called by) /home/teer/public_html/admin/includes/functions/database.php on line 51 <== in /home/teer/public_html/includes/classes/db/mysql/query_factory.php on line 171.

the files in question have not been touched.
Thanx
Mike

My SQL mode is

MySQL Mode: ONLY_FULL_GROUP_BY, STRICT_TRANS_TABLES, NO_ZERO_IN_DATE, NO_ZERO_DATE, ERROR_FOR_DIVISION_BY_ZERO, NO_AUTO_CREATE_USER, NO_ENGINE_SUBSTITUTION

is this the problem?

With PHPmyadmin
In the Categories Table I changed the Default value for the field categories_promotion_id from none to Null.
Everything is working now.
Why did i get this error now after many new categories were added?
thanx
Mike

The field categories_promotion_id is not native to Zen Cart, so it's not handled by the Zen Cart core code.
When you added it, it was added with no default, probably under MySQL 5.6.
Your hoster updated to MySQL 5.7. Now, this is not allowed - you either have to set the value in the insert, or say null is allowed, or have a default value.

That's why.