Have you ever gotten this timestamp error after making a deposit?
<msg>Record not processed because submitted version: is less or equal to previously submitted version </msg>
Yes? Then you are in the right place to solve this error!
Essentially, this timestamp error implies that the DOI you are attempting to deposit is already registered, and that the current timestamp in your deposit is numerically lower than (or, equal to) the timestamp used in a previous deposit.
Let’s pause here for a minute 
Why do timestamps exist?
You might be asking yourself: why does Crossref do this? Well, we have some members who register hundreds or even thousands of DOIs each day - sometimes the order in which those submissions enter our submission queue may vary from what was intended by the member. Long ago we decided to build in a check that ensured that the most-recently processed submission was indeed the most up-to-date version of the metadata. Using a timestamp in the submission ensures that the submission being processed is the newest and indeed an intended update (we’re not overwriting a metadata record with an older, previous submission).
Therefore, if you got this error, and you do not intend to perform a metadata update (meaning the metadata and URLs previously deposited for the DOIs are correct), then no further action is needed. You can stop here, and ignore the error.
No, I really do want to update the metadata!
However, if you intend on performing a metadata update, let’s continue.
There are two possible ways to solve this timestamp error:
Option 1: Increment the timestamp value in your deposit
You can increase the timestamp value in your deposit, to a higher value. For example, if the timestamp value in your previous deposit is 20220706100205988, you can simply increase the timestamp value for the new deposit to 20220706100205989 (by just increasing the value of the last digit from 8, to 9). This solves the error.
Option 2: Request for a timestamp reset to your DOIs (Highly encouraged for updates exceeding 200 DOIs)
If you recently underwent a platform migration, then you can request that we reset the timestamp values for your previously registered DOIs. You can send us a list of the affected DOI(s) to support@crossref.org, and we will assist you in resetting their timestamps from our end.
That done, this should solve your timestamp errors!
Thanks for reading.
Evans