WooCommerce shipping issue
I have one issue in WooCommerce when user apply the coupon then while checkout page showing invalid shipping method and when not apply coupon then it's working perfect.
I had the same issue just the other day. I take it you are using some sort of table based shipping?
If so the new total (after the coupon has been deducted) might not be included withing your table rate shipping.
To fix this, add a rate of shipping for £0 - to say £10 and give that the same priced shipping as your lowest rate.
I hope this makes sense?