As per reasonable notice - they have to receive the notice and delivery times have to be taken into account. I’m assuming you sent a letter requesting the return of the property and didn’t rely on a support ticket that clearly states it won’t be answered for 20+ days ? Or do you serve your notices via social media on third party sites?
Key words - “reasonable notice”.
It is also reasonable to look at a legal contractual term called “performance”. When a company is experiencing technical difficulties “performance” may not be possible.