Not sure if you were sent a different code but one I've seen is "20EVERYTHING1" as below - not 4 on the end?
T's and C's also below.
Says no product exclusions but also says it won't combine with any other offer, so I don't know if it will work with the monthly skincare offer, for example (hope not as I bought it end of last week - though I did get £4 off it!)
NB. Also there is site-wide free delivery until midnight Tuesday 4th June...
This discount code has no product exclusions. Discount code valid online at uk.lizearle.com and through our Customer Centre. Please immediately quote code 20EVERYTHING1 when ordering through our Customer Centre. This coupon code is valid until the 9th June 2019 and cannot be used in conjunction with any other sale or promotional offer. Discount code may only be used once per customer and must be entered at your shopping bag prior to checkout. Subject to availability. No cash alternative.