The Russian SFSR was not invited to attend, having already concluded a peace treaty with the Central Powers in the spring of 1918.
The Central Powers - Austria-Hungary, Germany, Bulgaria and the Ottoman Empire - were not allowed to attend the conference until after the details of all the peace treaties had been elaborated and agreed upon.
[1] Despite not signing the treaties, other delegations were sent to the Paris Peace Conferences, some uninvited, in order to represent their national interests.
Vosugh od-Dowleh Mohammad Ali Foroughi Other non-national or pan-national delegations were in Paris, hoping to petition the allies on issues relating to their causes.
[34] In 2014, the news outlet Ràdio i Televisió d'Andorra investigated the 1958 claim and could find no documentation of any original declaration of war.