Since I haven't written it elsewhere, I'll write up my recent voting experience here. I'm registered as a "No Party Preference" (NPP) vote-by-mail voter living in Contra Costa County, California. As an non-partisan ballot, (logically) that ballot did not include the ability to vote in any presidential primary. But the rules of some parties in California (Democratic, Green, and Libertarian) allow you to vote in their primary as an NPP voter if you exchange your NPP ballot for a "crossover" ballot.

Shortly before the primary election, the California Secretary of State issued a clarifying statement about how the process worked for NPP voters. It included these options for NPP voters who wanted to vote in a primary:

Contact your county elections office no later than May 31
to request a [party specific] vote-by-mail ballot... OR

Bring your vote-by-mail ballot to an early voting location
or the polls on Election Day and exchange it for a ballot
with presidential candidates

NOTE: If you have lost your original vote-by-mail ballot,
you will have to vote a provisional ballot at the polls—your
vote will still be counted.

http://www.sos.ca.gov/administration/news-releases-and-advis...

Since I was planning to vote in person anyway, and since I wanted to vote in the Democratic primary, I decided to bring my valid vote-by-mail ballot with me to exchange for a standard non-provisional Democratic party ballot at my assigned polling place.

When I got there (the lobby of the local Catholic church), I waited (briefly) in line, presented my mail-in ballot, and was told that exchanges for Democratic ballots were not being allowed. I mentioned the Secretary of States memo, and was (politely) told by the volunteer at the desk that they they knew nothing of this, and had been instructed that only provisional ballots were to be given.

Not wanting to hold other people up, and not wanting to accept a provisional ballot that would not show up in the end-of-day count, I left my place in line, went outside, and researched my options on my cell phone.

I discovered that indeed, Contra Costa County historically has had a policy of not exchanging mail in NPP ballots for "real" partisan ballots, that the Secretary of State's memo was part of the attempt to make clear that this was against state law, and that the day before the election the County had begrudgingly agreed to temporarily change its policy:

After hearing reports of Contra Costa County’s practice,
the Secretary of State’s Office contacted local elections
officials. On Monday, they announced they would change
their practice and offer these voters replacement ballots.

http://ww2.kqed.org/news/2016/06/07/contra-costa-county-at-o...

But apparently no one had told the volunteers working at the polls!

So seeing no way to solve this on my own, I went though the line again, and accepted a Democratic "provisional" ballot. I was told that I needed to take the "provisional voting class", and directed to a table with 4 or 5 confused people already seated at it. A few minutes later, another volunteer (elderly, bewildered, apparently having a very hard day) tried unsuccessfully to give us instructions on how to fill out the form on which we were to affirm our identity, electoral status, and reason for requesting a provisional ballot.

Then the volunteer left, and we filled out the forms as best we could. The process was sufficiently confusing that one of the voters gave up and left. After 5 minutes, the volunteer returned, and then mentioned that I wasn't supposed to have filled out the line that said "Reason for requesting provisional ballot", crossed out my complicated answer.

He then went to fetch the actual ballots for us. Most of us filled them out at the table, although I think one person went to a voting booth to do so. A second person gave up at this time. Or maybe they hadn't understood that they were supposed to sign and seal the envelope and drop it in the box on the way out? Or maybe they had to go to the bathroom and planned to return.

Eventually, the volunteer returned and I was told I was told to tear off the "receipt" from the provisional ballot and drop the ballot itself in an official looking bag next to the exit. The instructions on the receipt said that after 30 days, I could check online or by phone to see whether my ballot was accepted.

I came home, and immediately filled out and faxed a Voter Complaint form, which I hoped the State would be sympathetic too as the County was directly disobeying their directives and failing to uphold their agreement: http://www.sos.ca.gov/elections/additional-elections-informa...

I never heard back any followup from the complaint. I've checked online several times, but 45 days later it still shows up as "No ballot found". That's right, so far as I can tell my vote was neither counted nor rejected, just lost. I might try phoning or going in person to see if I can learn more, but at this point I feel it's a lost cause.

Edit: I should point out that I don't blame the volunteers --- they were poorly trained, and doing as they are told. But why are we relying on poorly trained volunteers for our elections? I do blame the County, since they failed to follow through on their pledge to the State and the press, but assume this is mostly poor communication rather than any specific ill-intent.