I ran a WooCommerce update on an old website the other day, and brought it up to v2.6.2. Everything seemed to go fine, except for the product archive pages, which changed from having five products in a row to alternately displaying products in rows of two and three. Luckily I found an easy fix.
The cause of this problem isn’t, strangely enough, related to archive-product.php, which might be your first guess, but is actually caused by content-product.php, the contents of which are pulled into the archive pages. If you’ve previously modified this file and stored a copy in the /woocommerce folder within your theme directory, you will probably find that it’s now out of date, and that’s what’s causing this issue.
All you need to do is grab a copy of your modified content-product.php, and make a note of any of the HTML/PHP adjustments you have made. Then, rename this file to content-product.bak. Now, go to the /plugins/woocommerce folder, and grab a copy of the latest version of content-product.php. Add your modifications to this, and upload it to the /your-theme/woocommerce/ directory. As long as you’ve copied across your modifications correctly, your products show show as intended in the correct number of rows.
If you have tried this and still don’t get any luck, try leaving a comment and we’ll see if we can help.