After updating theme X from 7.*** version to the latest one 8.0.9 today the site giving me fatal error, there was mention of wp estimation in that error
first, i deactivated wp estimation plugin, site works. Later on, I found this thread WP Cost Estimation & Payment Forms Builder Plugin not working
so as per thread above i have activated again my WP cost estimation plugin so fatal error reappeared
but begin deactivating the other plugin. My first deactivation on the list Contact Form 7 gives me the result and the site is working.
So it means WP Cost estimation and Contact Form 7 together is in conflict.