You have a choice, in the Confidence tab, to either mark entire fits as "ambiguous", to mark selected parameters as "unstable", or neither. The option to mark parameters as "unstable" is a new (in 8.2) feature from Prism Labs.

If you choose "unstable", Prism will identify any parameters that are unstable and write "(Very wide)" in place of the confidence intervals for those parameters.

If you choose "ambiguous", if the entire fit is ambiguous, all confidence intervals will be replaced with "(Very wide)".