how to re-enabled the threshold sp?

I have a threshold set on log segment with action procedure.

Then I increased log segment space and got message said the threshold disabled.

this is the info from

sp_helpthreshold 'logsegment'

go

Here is what I am trying to do: drop it and recreated it again:

---1. drop one, it is okay.

EXEC sp_dropthreshold 'mydb','logsegment',300000

go

--2. drop another one:

EXEC sp_dropthreshold 'mydb','logsegment',300016

go

---got followinng error message:

Procedure (sp_dropthreshold) You may not drop the log's last-chance threshold.

--3. try to put it back:

EXEC sp_addthreshold 'mydb','logsegment',300000,'dbo.sp_thresholdaction'

go

---got following message

Procedure (sp_addthreshold) This threshold is too close to one or more existing thresholds.  Thresholds must be no closer than 128 pages to each other.

How to resolve this problem?