Присоединяюсь к вопросу, такая же проблема на keenetic giga kn1010 с версией прошивки 5.0.10:
[I] Apr 22 09:59:08 ndm: Acme::Tools: requesting "https://acme-v02.api.letsencrypt.org/acme/order/38280124/503175225151"...
[I] Apr 22 09:59:08 ndm: Acme::V2: got result from server.
[I] Apr 22 09:59:08 ndm: Acme::Runner: downloading signed certificate chain...
[I] Apr 22 09:59:09 ndm: Acme::Tools: requesting "https://acme-v02.api.letsencrypt.org/acme/cert/06150bfef8ab6598cca2140266c2f24b3656"...
[I] Apr 22 09:59:09 ndm: Acme::Client: save certificate for domain "....keenetic.link" into persistent memory.
[C] Apr 22 09:59:09 ndm: Core::System::Mtd::ConfigImage: system failed [0xcffd03b3], no free space to store an extended entry (stream 8, entry 21, 11915 bytes).