I have made two travel insurance claims and helped friends with four more. Three of the six were rejected, and in every case the reason was something that could have been dealt with before departure.
This is a description of what has actually happened rather than advice about any particular policy. Cover varies enormously and the document you hold is the only thing that governs your situation.
Undisclosed medical history
The most common rejection by some distance, and the one people find most unfair.
Policies generally require disclosure of pre-existing conditions, and the definition is usually broader than people assume. It commonly includes conditions you have seen a doctor about within a stated period, whether or not they are ongoing, and whether or not they seem relevant.
The rejection that hit somebody I know involved a condition entirely unrelated to what they claimed for. The policy position was that non-disclosure invalidated the cover generally, not just for that condition.
Whether that is reasonable is a separate argument. The practical point is that disclosure costs a higher premium and non-disclosure risks the entire policy.
The activity exclusion list
Standard policies exclude a long list of activities and the list is longer than people expect.
It routinely includes things that do not feel adventurous — riding a moped, some winter sports, hiking above a stated altitude, and any activity described as an organised sport.
The moped one catches an enormous number of people, particularly in places where hiring one is the normal way to get around. Many policies exclude it entirely, and many others require a licence valid for that vehicle in that country, which a lot of people do not have.
Read the exclusion list before travelling, not before claiming. If something you plan to do is on it, the extension is usually inexpensive.
Alcohol
A clause in nearly every policy, excluding claims arising from incidents where the claimant had been drinking.
The wording varies from excessive consumption to any consumption, and the interpretation in practice is not generous.
This catches injuries in the evening, thefts from people who were out, and road incidents. Medical records frequently note alcohol involvement, and those records are what an insurer sees.
The reporting requirements
The one that has caught people I know twice, and it is entirely procedural.
Theft claims almost always require a police report, filed within a stated period, often twenty four hours.
Getting a police report abroad, in a language you do not speak, within a day, while dealing with having been robbed, is genuinely difficult, and a lot of people do not manage it. Without it the claim generally fails regardless of merit.
Similarly, many policies require you to contact the insurer's assistance line before receiving non-emergency treatment. Paying for treatment yourself and claiming afterwards can breach the terms even when the treatment was necessary and the cost reasonable.
Save the assistance number somewhere you can reach without your phone.
Unattended possessions
Policies define unattended in ways that surprise people.
A bag on a beach while you swim is unattended. A bag on the seat beside you while you look at your phone may be, depending on wording. Luggage in a locked car, in many policies, is excluded regardless of the lock, and almost universally excluded if visible.
Valuables left in accommodation without a safe are commonly excluded, and left in a safe are often covered up to a low limit.
The practical consequence is that the expensive things are frequently not covered in the situations where they are most likely to be taken.
Cancellation, and what counts
Standard cancellation cover applies to a specific list of reasons — illness, bereavement, jury service, certain employment situations.
It does not generally apply to changing your mind, to a destination becoming unappealing, or to disruption that does not meet a stated threshold.
Cover for cancellation for any reason exists, costs considerably more, and typically reimburses only a proportion. It is worth its price for expensive trips booked a long way ahead and not for much else.
What I do now
Read the exclusions before the benefits, because the exclusions are where the policy actually lives.
Disclose everything medical, and accept the premium.
Check every planned activity against the list, and extend where needed.
Save the assistance number and the policy number somewhere reachable without a phone.
Photograph valuables and keep receipts, because claims for items you cannot evidence are settled at whatever the insurer thinks they were worth.
And report anything to the police immediately, even when it seems futile, because the report is what makes the claim possible.
The one that succeeded
My own successful claim was medical, abroad, straightforward, and paid in full within about three weeks.
What made it work was calling the assistance line first, going where they directed me, and keeping every document.
Which is not clever. It is following the process, and the process is what the three rejected claims did not do.