Love this plugin It has worked really well and been reliable for the last years up I updated word press to V4.6.1 November 15th 2016 and woo-commerce to version 2.6.8.
After this new orders failed and customers were not able to recheck out.
The message customers got on screen when pressing Place order then checkout buttons was Oops something went wrong.
The weird thing is that it didn't make sense however what did make sense was that I also had the same plugin installed on 3 other users page and I did the same updates in the same evening.
Those sites also had the experience the following year on Nov. Oops something went wrong.
We're probably doing planned After allowing and deleting WooCommerce Sequential Order Numbers plugin on those sites too no further checkout issues happened.
I love this plugin It has been great for few years.
I'm sure this will be figured out and determined then so it can be uninstalled.
The developer is useful I hear and has great page on his blog.
Edited to add The processor on all three sites with the same file is PayPal Standard as is installed with woo finance.
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