Great Britain's bid to reach the Billie Jean King Cup play-offs started with defeat for Harriet Dart against the Czech Republic's Marketa Vondrousova.
Dart, 25, has been in decent form this year, but found it difficult on clay against the 2019 French Open runner-up.
Vondrousova, who is the home team's highest-ranked player in the Prague tie, won 6-1 6-0.
Emma Raducanu takes on faces world number 50 Tereza Martincova in Friday's second singles rubber.
US Open champion Raducanu will play her first senior match on clay, as well as making her debut in the Billie Jean King Cup.