I had the same problem. I disabled all the plugins, made no difference.
I then contacted my theme support Kadence Themes – Ascend Theme – who told me that their theme does not interfere with any woocommerce settings. They suggested I contact my e-mail host.
I contacted the e-mail host blacknight.com who told me that this is indeed a problem with woocommerce version 4 which has not been corrected.
They provided two work arounds – switch to plain text (which I had already done) or install an SMTP plugin. They had tested ‘Easy WP SMTP’
I installed this, switched back to SMTP emails in woocommerce and the problem is resolved.
You can read the blacknight article here – https://help.blacknight.com/hc/en-us/articles/360007089858-WooCommerce-Emails-Blank-Wrong-Formatting-Missing-Content
Hope this helps,
God bless
John
