The title is mainly clickbait. The bonds they’re talking about were sold in 1938 by the US backed Republic of China, which at the time was fighting a civil war with the Peoples Republic of China (Maoists). The RoC lost, and retreated to Taiwan. The PRoC then assumed control of the country, and decided that it wasn’t interested in paying the debts of the government it had just vanquished.

However, under international law, when the PRoC took over China, they also assumed responsibility for paying those bond holders. Nobody has gotten them to pay up except the UK when the transfer of Hong Kong was up for consideration.

So basically, this is a 70 year old debt that was taken out against China’s former government, and the current government really has no urgency to address it.

As @mazelado pointed out, this is an opinion piece by the Heritage Foundation, so the motivations in writing it are suspect, especially as it’s specifically pushing the Biden administration to fight this very old fight. You would have thought that if had really been a pressing matter, Trump would have handled it when he started the US / China tradewar right before COVID, as it was clear Don didn’t have any qualms pushing potentially destructive diplomatic policies that were unpopular to the Chinese.