В приложении видно, что товар есть в наличии, но на складе его пока не нашли.

Because в приложении answers the question where? — in the app. That requires the prepositional case after в.

• в приложении = in the app
• в приложение would suggest motion into the app, which does not fit here.

So this is a location, not a direction.

Видно here is an impersonal predicate. It means something like:

• it is visible
• it can be seen
• it is clear/apparent

Russian often uses impersonal constructions where English would use a full subject like it.

So:

• В приложении видно, что... = In the app, it can be seen that...
• more naturally: The app shows that...

There is no explicit subject because Russian does not need one in this kind of sentence.

Что introduces a subordinate clause: that ...

• видно, что товар есть в наличии = it is visible/apparent that the item is in stock

So что connects the main idea to the content being observed.

Both are possible, but есть emphasizes the existence/availability of the item.

In Russian, the verb to be in the present tense is often omitted, but есть is still used when you want to stress that something exists / is available / is present.

So:

• товар в наличии = the item is in stock
• товар есть в наличии = the item is indeed available / there is stock of the item

In this context, есть sounds natural because the sentence is about whether the item is actually available.

В наличии is a fixed expression meaning:

• in stock
• available
• on hand

It is very common in shopping, inventory, and customer-service language.

Examples:

• Товара нет в наличии. = The item is out of stock.
• Есть в наличии? = Is it in stock?

Russian normally says на складе for in/at the warehouse. This is just the standard idiomatic choice.

Even though English says in the warehouse, Russian uses на with some places and institutions where English might use in.

So you should learn it as a set phrase:

• на складе = in/at the warehouse

Его refers back to товар.

• товар is masculine singular
• in the second clause, it is the direct object of нашли
• therefore it must be in the accusative case

For a masculine inanimate noun like товар, the accusative form is the same as the nominative. The pronoun is:

• он = he/it
• его = him/it

So:

• его не нашли = they haven’t found it

There is no explicit subject, but the verb in 3rd person plural past often means an indefinite human subject:

• не нашли = they didn’t find
• but not necessarily a specific they

In English, this often corresponds to:

• they haven’t found it
• it hasn’t been found
• the warehouse staff haven’t found it

Russian uses this structure a lot when the doer is unknown, obvious, or unimportant.

Нашли is the perfective past form of найти (to find). With negation, it usually means:

• did not find
• have not found
• failed to find

It focuses on the result: the item is still not found.

By contrast:

• не находили would sound more like were not finding / did not find on some occasion(s) or would emphasize repeated attempts/process, depending on context.

Here the important point is the current outcome, so не нашли is the natural choice.

Here пока means:

• for now
• yet
• so far

So:

• его пока не нашли = they haven’t found it yet / so far

It suggests the situation may change later: they might still find it.

Но means but and introduces a contrast:

• the app shows the item is in stock
• but the warehouse has not found it yet

So the sentence contrasts system information with real warehouse reality.

Yes, but mostly for emphasis rather than basic meaning.

• В приложении видно... puts the focus first on where this information is seen: in the app.
• на складе его пока не нашли puts на складе early to highlight that the problem is specifically at the warehouse.

A more neutral order might be possible, but this version sounds natural and helps organize the contrast:

• In the app...
• but at the warehouse...

Yes. The Russian second clause is active in form but indefinite in subject:

• его пока не нашли

English can translate that in two natural ways:

• they haven’t found it yet
• it hasn’t been found yet

Both match the Russian meaning. Russian often prefers this 3rd person plural with no named subject, while English often switches to the passive.