Could not load type 'Sitecore.Links.UrlBuilders.ItemUrlBuilder'


I'm a Sitecore newbie. This is my fourth day trying to follow the trail: Developer's Fundamentals 9.3 Collection.
Right now I'm facing an error related to a failed attempt to load type 'Sitecore.Links.UrlBuilders.ItemUrlBuilder'b when I tried to do Serialization (Item Serialization -> Yaml Serialization) following the instructions provided by the Instruction Lab.
Everything was working fine on my site (, but then after building the solution, this errors appeared:

Does any of you know why is this happening and how to fix this issue?
Thanks in advance.