Riot Games, the small indie company, is still having issues with League of Legends' client but the more pressing issue emerged recently when match history disappeared. The team confirmed it is being handled and slowly put back in.
League's client has been problematic for years and is getting some background fixes but it may still be some time until they are deployed. A more immediate matter happened a while back when the players could no longer see match history.
While this does not make the game unplayable, it did have a severe effect on analysing the performance of those who wished to improve upon their skills that way.
On 11 April 2020, Mark "Riot Scruffy" Yetter informed his Twitter followers that the developers are slowly putting the feature back into the client. Some players should be seeing match history at the time of writing, with more and more as time goes on. Riot's plan is to have it fully functioning again in the following week.
Some players are still worried about other bugs plaguing the client, such as freezing in champion select which forces the players to dodge a match. This isn't that horrible in regular games but in ranked, it imposes loss of LP on top of the regular punishments. At least they backed away from making the queue dodge punishments harsher for the time being.
Riot Games moved to the full remote work setup when Covid-19 wreaked havoc on the infrastructure of companies in the entire world, which may have affected the team's ability to keep up with the client updates and maintenance as they are also working on several other projects, such as new champions or the reworks of the older ones.