Cannot access trend archive

First of all, for critical issues please contact Support. Better not to rely on a user based forum.

My 2 cents:

Is the trend stored on a local drive or network share?

If on a local drive: please verify the drive health. Might be a hardware issue.

If on a network share: could be several reasons, like a disconnected drive mapping (shown in Windows as a red cross along the drive letter), or a network performance issue.

It could also be a lack of permissions to the data path, but you mention that if you retry some data is logged, so that is unlikely.

It could also be a trend file corruption.

As you can see, it might be several things. Hard to tell without more info.

If this error only occurs to Trend SC1_CH1_PV, it is highly likely its trend files were corrupted, as Patrick pointed out. The other possibility is that the configuration of this trend has been changed, such as sample rate or storage files, and etc. 

Trend store in local drive.

Trend Type - TRN_EVENT;